No, insofar as it would be so hard to get off the ground commercially. There's already a business alternative in LinkedIn, and a lot of communities (eg Metafilter or various specialist discussion forums) already have the rudiments of a network in place.

I'm rather surprised nobody has made a peer authentication thing for PHP-BB or similar, so that members of on one of the many forums running on this platform can 'visit' another website and cross-post, if you see what I mean.

for that matter I'm surprised Google Wave hasn't been polished up yet - you'd think Google would take advantage of their enormous user base and prior experience with Orkut and Buzz etc. to offer robust group communication with the requisite privacy controls by now. It's not like they don't have all the necessary components.