After much deliberation, I deleted my Facebook account around 1.5 years ago. I even ensure that nothing from Facebook can be accessed from my computer.
Like you, I have lost out on the weak ties, but have decided that I would rather lose those than let Facebook know everything in my personal life and my activities on the web.
I'm trying to find some middle ground. For example, I use Ghostery to block Facebook comments and like buttons, so they're not aware of my activities on the web. And I've used a special email just to sign up for Facebook, so people don't find me there unless I want them to. I'm not friending everyone I know, only the weak ties I don't have a better way to keep up with (i.e. they aren't on Twitter or something else).
Not sure how it'll work out long run, but right now Facebook knows very little about me.
Like you, I have lost out on the weak ties, but have decided that I would rather lose those than let Facebook know everything in my personal life and my activities on the web.