Marc Canter is probably like the guy who saw the Bering land bridge form and yelled "Hey, guys!  Lets go across!"  He joined LinkedIn and invited 50 people.  I am too lazy to do that.  Its too much work to think about who I know, whether I should invite them, and to find and type in information.  LinkedIn should make it easier to invite.

One way to make it really easy to invite people is to leverage the informal network already formed in Blogland: blogrolls, links, trackbacks, and comments.  Given my blog's URL, a list of candidates for invitation should come up.  Even if some of them already joined, I want to know about it.  Best way to form new network is to add them in natural groups so they can support each other.  Come on Reid, this is no brainer.  Just swallow the whole Blogland a juicy cluster at a time!

A tip on subscription-based revenue model: make it free for and offer extra goodies to Connectors (as in Tipping Point).  This is how hunters catch whole herds.