You know Matt, I don't think you would be concidered a jerk by announcing your weight loss to your FB friends. I did, (pretty generic actually...just said I finally reached my goal weight.) and it felt good. I received many notes and comments but I also received several PM's from friends wanting to know more about my situation and plan of action. For those who requested more info I sent them a link to my goal story that I used to have here at 3FC. Just recently I received a note from an old high school friend that was so inspired by my story and pictures that he decided to lose weight too and has now lost almost 60 pounds, (with 40 more to go) in the last year. I was THRILLED.
My point is, if you can inspire ONE person...just one, to get healthy and live a better and more productive life, than it totally outweighs any jerk who thinks you are a jerk!
Go for it!