Yeah, they're about to re-launch groups and give Facebook groups a run for their money, too. Starting yesterday, group notifications are apparently showing up more prominently in your feeds, and there are a few more changes on the way.
Given that FB Groups have become popular with businesses because they force notifications to members (whereas business pages continue to become more pay to play), this could be a really interesting development.
RE: Growth Hack: Exploiting LinkedIn's Network Effect for Maximum Reach