When it first started and I was starting to "network", I thought it was great and helpful. However, one day a wholesale customer of mine asked for an invite. At the moment, I thought "why the heck would I give you access to all of MY contacts?". Shortly after that, another wholesale customer did the same thing. I was a little bit offended that someone would be so bold as to ask me to hand my business contacts over to them for free.
I had no issues sharing with people in different businesses, but I have a fairly big issue with handing my contacts over to my competitors for free.
And yes, I get really odd ones that have no connection, it's just someone trying to build up their count.