1) For flights to SoCal, I try to get to the airport 15 minutes before pushback. My theory there is that if I allow too much time, I might as well drive. Plus, you get better info on delays the longer you wait.
2) For other domestic flights out of SJC, I give myself 30 minutes whenever possible because eastbound flights are fewer and often more crowded then intra-Cal flights.
3) For international flights out of SFO, 45 minutes is my rule of thumb.

Why I cut it close?
-As much as I like flying, I'd much rather hang out at my house or office than the airport (including those lounges).
-My dad was always super anal about this topic when I was little (e.g. getting to the airport 3 hours before the domestic leg of a trip to Canada!) and it always irked me.