Ok...I'll admit to being a LinkedIn spammer!
- don't invite someone who isn't already on it and reasonably active.
- don't invite, or accept an invite from, someone whom I haven't already had a businessy email exchange/conversation or is already a friend.
The reason: once you hit 500 connections on LinkedIn, they stop showing the number of your connections to others, and just keep it at 500+. So at the start of the week, when I saw that I was at 493 connections, I just couldn't resist the idea of joining the 500+ club.:)
You probably wouldn't ask, so let me just tell you: yup, I'm in now.:)
True story: just before leaving the Bay Area to go to b-school two years, when my LinkedIn connections were still in the low 2 digits, someone actually said to me, "Don't come back as one of those MBAs who have 200+ LinkedIn connections."