That totally sux. Thing is, back in high school I had a system jacked with an alarm and it even had the pager. I never got paged because I was in class (apparently out of range), and they just ripped out the siren. They took 6 Solobaric 12's, an A404 and 3-A600's. Thing is, if they want it, they'll get it. I only had it installed for 1 month.
Earlier that year I was even carjacked at gunpoint in my high school parking lot. The guy took off with me in my truck and I later jumped out. I had LoJack and 10 minutes later, he was off to jail for 15 years. Sucka.
From what I hear, it's often times people who know of you/have seen you around at the local car club meetings/shows or wile you're cruising around town.