At Linkedin you are the product. Don't ever think otherwise. They are mercenaries about building up the social graph because it is how they build up the data they need to sell to the job spammers. The biggest "secret" of LI is that you get a score based on the "quality" of the people you are linked to. Know lots of ivy leaguers and fancy MBAs? You get a +10 bonus. Rockstar talent with no high rated buddies to link to? -10 for you.