Creative Capital got ahold of the December 2007 ComScore numbers for the top social networks in the U.S. — and they are, on the whole, not good. Engagement — average minutes spent on the site per visitor — is down for MySpace and Microsoft's Live Spaces, but up for almost all the other sites. Unique visitor growth is ominously low for MySpace and, in the last three months, LinkedIn. Hit the jump to see the numbers for yourself.