Here's a great infographic from Vincenzo Cosenza that details how many users LinkedIn has, including how many from Canada, US, UK and other parts of the world. Also noteworthy is the list of top job sectors.

I'm a terrible focus group of one, but I use LinkedIn primarily for parking my professional contacts, though it is great for getting scouting reports on clients (complete with headshots) and potential recruits (when you want to go beyond the supplied references.)

If you want to share this infographic easily, Vincenzo's made the code snippet available on his blog:

The State of LinkedIn 2011