Modern art should make you chuckle at how clever it is, or make you marvel at who something so simple has changed so much in a new perspective. Things like the urinal on its side and the tar room are a marvel to see and really are clever pieces of work.
Making a light turn on and off is a load of bullcrap. There are very few modern artists who are actually decent.
There are always acceptions to this, but for the most part, I really can't get into the whole "look! I've flung paint randomly!" that the rich people run up to and say "BRILLIANT! I'll take it!" Groxx, you said it best, the name's selling...or the fad is selling, but not the works.
Well, it really depends upon the piece in particular but if you're just going for a generaliaztion, I would say that i thas it's place and that for the most part the artists are trying just a little to hard to be different. Still, there are certainly pieces that are head and shoulders above conventional works. Essentially, it's all really instance specific.
the category "Modern Art" is so incredibly broad, I don't think this really fits that well.
Some, I like. There are certain styles/people that always have great stuff, and there's some things where it's just a bunch of circles, totally abstractly placed. The ones that are obviously totally random, I honestly hate. Those sell because the "artist" is selling his name, not his works.