It's a question I asked on LinkedIn itself the other day and unsurprisingly unanimously the answer was Linked In for business, Facebook for personal. I expanded and asked if others were using Twitter or Friendfeed or any other social network and again the majority response was I don't have time (Now that's a whole different post).
The reason I asked in the first place was I just can't get along with Linked In. I'm a big fan of social networking and in terms of it's educative qualities it's been an enormous addition to my professional development. Twitter has almost completely surplanted my RSS feedreader as a research tool. Friendfeed helps me to understand who influences those that I choose to follow. Facebook keeps me in touch with friends who due to family pressure I don't get to see much and cousins I don't see regularly, you know the score. Delicious and Digg help me to share my bookmarks and content I like.
All of these platforms help me be social and hopefully helpful. They allow me to be myself but also keep on top of business and that's where I part the way with LinkedIn. It's not a social networking site, nothing about it is social. It's about networking, but not the ecademy way, it's more the bad glass of sweet white wine and guard up kind of way. It's not intuitive, it doesn't aid in the sharing of information, in essence it's far too closed.
I concede that it is great at finding professionals and if you are looking for a job, but Twitter and Friendfeed do that as well as everything else and as an added bonus you're likely to understand whether you'll get on with them on personal level as well which for me is just as important.
In my opinion it really needs to step up it's game if it's going to continue to grow, there are rumblings that there is a major overhaul in the planning stage, I just hope it's a significant improvement.