Examples of BAD modern design?  

It IS a bit much
Not everyone's taste, to be sure, but at least it does what it was designed to do.
What I consider "bad" design I break down into two categories:
1. Designs that work well, but are not my taste (I don't personally like chair legs that splay out too much, for example, the Poul Kjaerholm metal legged chairs) I wouldn't want them, but if I were teaching a class on good modern design, my opinion would be set aside and I would not impose it.
2. Items that were designed to look good but do not work in a real life setting (goofy chairs like Roberto Sebastian Matta's "Mararita" chair, Gaetano Pesce's "Sit Down chair" or Gruppo's "Memoria" chair may be iconic designs, but they belong in a museum and not in someone's home!)
Putting my personal tastes aside, I would classify "bad" design (at least as regards furniture) to be something that despite its appearance doesn't work because it's either uncomfortable, poorly constructed, overly complicated to use, or simply doesn't hold up well to normal usage.
Most of the "good stuff" has weathered the test of time. When I started furnishing my home, I bought a lot of books and there IS a concensious about what's good and what's not. (It amazes me that after 70+ years, Aalto, Le Courbusier, Bruer, van der Rohe, and Eileen Gray's stuff STILL looks fresh, modern and beautiful. Heck, even Josef Hoffman's Kubus chair and sofa from the 1920's looks beautiful and fresh alongside, say, an Eames Lounge chair and ottoman!!)
Good and bad design has a lot of personal opinion and taste, but clearly, if it's not convenient to USE, then in my opinion, it's not SUCCESSFUL good design.....unless you have it roped off in a museum setting.

hmm...
I wouldn't exactly call it 'bad' modern design. Granted, it is not to my taste. I find it a bit ugly, but it suits it's purpose well. IMHO, 'bad' modern design is any piece that is not functional. For example, a chair that looks cool but no one will ever sit in because it will give you a sore back and butt every time. I'm not really a fan of 'museum' pieces of furniture...pieces that are designed to only really be looked at but not used. Anyway, I think there is a differnece between bad design and ugly design(by my tastes anyhow). I'm sure there is someone out there who really thinks that entertainment system is totally cool-looking.

remember kids....
...
remember kids....
that is what makes the world go round...
every one likes something different.

I was trying to
make a distinction between stuff I think is ugly (purely personal taste) and stuff I think is either poorly designed or (in the case of furniture and lighting) uncomfortable to sit on, made with crappy materials, or too difficult to maintain.
To me, there's a difference.
Another example of silly design is the iconic Marilyn sofa. Nice to look at but how usable is it?
The Joe sofa? Is it comfortable? Would it look nice next to a Florence Knoll coffee table?

TV cabinet
The TV cabinet reminds me of this firewood holder. I probably wouldn't use it for a TV. As for poor modern design, the Multipot(USA) gets my vote. Looks great, but the plugs are too close to allow more than a couple small electronics with the larger plugs. Also the cord isn't very flexible and they should have used a flat wall plug.

That does look alot like the...
That does look alot like the TV cabinet. Looks good holding wood...not so much as a TV cabinet though.

Failure vs. bad design.
Every stellar designer should have books of bad designs. Its just the nature of problem solving that leads designers to reiterate and tweak and improve upon. It would be a horribly arrogant designer that could claim he has not made any mistakes.
But there is also a big difference between a bad design and a failure. A failure can be anything that did not meet the original criteria, whereas a bad design is generally something that just doesnt function very well. For example, the Eames plywood lounge was originally conceived as having a single piece shell rather than a separate seat and back. While a failure of the original intent, the LCW is nonetheless a great design.
I think my favorite example of a bad design is Bertoia's side chair. As beautiful as any of his other wire chairs - the side chair has a quite uncomfortable sit, especially without a full cover.

I'm sure that entertainment u...
I'm sure that entertainment unit does look cool to some. I'm not sure if they'd be over 14. Maybe retired freighter captains sweet on seeing a ship's porthole in the living room. Of course, everyone has different tastes. I read a blog yesterday where they were trashing some hollywood celeb to bits, after seeing a photo of her with a sputnik lamp in her hand. Although I find the tv unit ugly as heck, that's only part of why I think its a bad design. For what it is and the size of it, I don't think its very functional. Besides being completely devoid of grace, it has no regard for the use of space.
Aesthetically, not to mention physically, it takes up a LOT of space. But look how it uses that space.... Since most tv's are not round, you can only use a small set (which are out of vogue), within the space assigned for it. Seems to me, anyone who can afford the $1500 price tag of the tv cabinet, can afford a larger set - and would want one. Again, because of the heavy rounding, the remaining space on that shelf doesn't leave room for much else. It even appears there is space on either side (behind wood panels) that cant be used. The bottom half isn't any more cleverly designed. For one thing, not too much electronic equipment comes with a hump in the center. So anything that extends beyond the center drawer hump (ie. a wide dvd player) will not be sitting flat. Plus, most of the space there is wasted, as there's no extra shelf. Then there's that awful center drawer, which takes up all that space just to be round, but doesn't hold much in the end. And if the whole thing doesn't take up enough room visually, wait til you watch tv with the doors open.
I find the round unit holding firewood a perfectly good use of that furniture shape. Not only does it look good (helped by a gorgeous surrounding), it does not look like its trying to be something it isn't. It makes good use of its space, you can pack it entirely up with firewood, without wasting the space it has. Nor does it look awkward when it isn't filled up.

my vote goes to the...
Barcelona chair - the most uncomfortable chair ever designed.
Starck citrus squeezer - doesn't actually work, unlessyou like juice all over your benchtop instead of in the glass.
Tizio Lamp - fails time and time again due to poor design at the joints - they corrode. I bought one of these pieces of cr*p on Ebay. surprise surprise, it didn't work. Took it to a lighting specialist in Sydney. He laughed and took me to a store room where he had literally hundreds of the things that were good for nothing but spare parts.
Schultz outdoor setting from 1966 - doesn't last outdoors in the Australian sun.

and the bankers clock
Oh yes,,,and the famous bankers clock by Jacobsen. Mine doesn't keep time no matter how many times I change the batteries.

change the movement they ...
change the movement they cost 5 dollars,

.
This look was fully explored in the 1930s ,I have seen far worse...but its has the LOOK! at this aura about it...

Stephen
Barcelona is a good design. The function of the Barcelona was to seat Spanish royalty for a very short amount of time. In that it is very successful as a design. To use a less graceful example - would you consider sitting on your toilet all day? Of course not, thats not its intended purpose. Its used for short sittings.

don't you mean...
short sh**ings?
I take your point LuziferSam
But I will maintain my rage against a design that sells for thousands of dollars and can only be tolerated for three minute intervals.
S