Not sure if my experience is common or rare, but since moving to California in 1993 and registering as a voter and a driver (the two lists from which they pull prospective jurors, as I understand it), I have been called for jury duty every 3 years like clockwork. You can opt out if you have already served in the last 3 years, but it seems like every time my anniversary passes I get another summons to serve. Furthermore, most of the time I have been called to sit in the jury pool in a courtroom, and on most of those occasions I have been seated as a primary or alternate juror. If I am counting correctly, I have deliberated on 5 cases (one criminal and 4 civil) and was a juror in one criminal mistrial that never made it to the deliberation phase. I recently received my latest summons, and for the first time returned it with an excuse: I am presently the stay-at-home care giver for our two kids and finding child care for 2 weeks would be a serious hardship. I don't feel bad at all about opting out this time.
As for those who casually brag about getting out of jury duty by claiming partiality or just by being an engineer (since the conventional wisdom is that neither side in a trial wants someone who can piece the facts together on their own), I call bull. Every judge I have ever sat before has grilled prospective jurors that claim they have some reason to be partial to one side or the other. They always end with the bottom line question: "Do you think you can be impartial in this case?" And answering no doesn't guarantee a dismissal from the jury pool.