Talking on your cell phone in public. This is so 1990's valley girl. It's completely uncouth and shows a complete lack of manners and refinement. It's roughly equivalent to cutting your nails or picking your nose in public. Bluetooth conversations are even worse.
Showing off your hi-tech gadgets. Gadgets are no longer cool. Technology is not amazing. If it's an effective tool for helping you live better, then use it to live better. The gadget is no longer and end in itself, it is a means. Are you going to show off how amazing scissors are next? Get over it.
Talking about Myspace or Facebook or pretty much anything on the internet. ZOMG you do stuff on the interweb? What's that? How fascinating and unique. Oh wait, no it's neither fascinating nor unique. Yes we all have fucking blogs and we read blogs, but we don't talk about it. This is akin to recounting the plot of your favorite TV shows. It's a mindless pleasure that you can indulge at home alone.
Snarky comments making fun of others. Your attempts at humorous condescension just sound like bitterness and pessimism; they aren't as funny as you think, and we've all thought of it before. In the rare case that you actually capture les mots justes to really skewer someone, then go ahead, but you probably didn't. We're all ridiculous, they're just trying to live.
Complaining about Windows or C++ or the US government or how dumb the populace is. Yeah yeah, it sucks, whatever. That's not interesting. If you'd like we can talk about concrete practical ways that we can improve our programming environment despite the suckitude of Windows and C++, or we can talk about how we can improve America despite our broken system.
Making lists of stuff that's over. Also, writing douchey things but then mocking yourself to try to absolve the sin.