My primary instrument is keyboards and piano, so I obviously take piles and piles of lessons for that, plus music college but I own a guitar and while I'm not very good, (Playing for about a year, maybe 2 hours a week tops) everything I've learned is self-taught, or I asked some of my guitar-savvy buddies for tips. Workign in a guitar store is good that way.
Of course, the theory skills I got from piano certainly helped a huge amount. If I were actually interested in becoming a truely skilled guitarist, I think I may have to get lessons or at least seriously push myself at home for hours on end daily.
I don't know about you guys, but I learn best from other people in a one-on-one situation. I particularily learn best by watching someone else do something and then trying to imitate their technique on my own.