I know I am really late in on this conversation, but from my observations I've seen LI being used for networking just as much as Twitter, it's just not as "friendly/friendshippy" as other options out there. I know a lot of boutique business folks (home businesses) who use it as a tool to increase their profile with other businesses. I've connected with a few other photographers there. Mostly it's a business networking site more than a social one but you can garner a following, pretty much like everywhere else.

I suppose it's all about picking your audience.

*slithers off*