There have been a ton of business social networking sites, but LinkedIn has simply gotten the most VC funding from Sand Hill Road...so they've hired the best talent and can afford the most effective marketing.  LinkedIn will be around for quite some time to come...

If you're interested in rubbing elbows with America's elite, try and get an invite to Small World.  It's essentially a social network for the rich and fabulous, and you can't get in unless you know someone who's already a member.  VERY exclusive.  Good luck!

 ~Pun Out