but why?  

This was on dezeen:
"London designer James Laurie has cut the top of a drinking glass into a point so that it can be used to trap spiders in the corner of a room. Called 'Cornered', the tumbler can still be used for drinking."
But isn't it much more difficult now, to slide the piece of paper to trap the spider for later release?
And still be used for drinking? Really?
http://www.dezeen.com/2010/03/29/cornered-by-james-laurie/

I would never drink out of a ...
I would never drink out of a glass that I used to trap a spider. Even after scrubbing multiple times. Yeck.

And what happens if the...
And what happens if the spider's in a corner near the ceiling or floor? or on a flat wall!?! how many glasses does this endeavor require?