I've got an Fb account, and I do use it lightly. I tend to have random conversations with people because of posts they make on twitter, or on their blogs.
I do watch my Fb news feed on my phone, so if I spot something worth starting up a conversation about I have the opportunity to.
My discomfort with Fb is that to even view content requires an account. Content is only shared amongst account holders. If I post some photos, or an event I don't want to require people to sign up to Fb to view that content. Hence I post my content on more open services. My concern is more for the other people who don't use Fb than it is for myself or those who already use Fb.
If I post content on a blog, I sometimes post a link on Fb. I don't see any problem with that. Some people choose to follow me via Fb, and that is fine, but I also want to remain open to those people who don't like Fb and I give them the option to follow me in other ways.