I can't speak to whether these sort of incidents get an exaggerated or unfair amount of coverage, or if these really are common problems. Of course either way, these sort of incidents/articles surely shape public perception; I don't think we can make this as simple as "Techies are nouveau riche who like to kick 'em when they're down".
They do get an exaggerated coverage. It's really not that common. I've been riding BART to/from SF for my techie-job for 6+ years and I haven't seen anything like that. The most interesting thing I've seen in person is this guy: http://www.youtube.com/watch?v=MGkbJlmhI90
Oh and I did see a guy yell at and punch a window on the BART train once for no apparent reason. It was late at night so not many people on the train but the few passengers were definitely freaked out. Window didn't even crack and he punched it HARD.
