So the new app on the Facebook block is the Visa Business Network. It's interesting because it isn't in fact a direct analogue of LinkedIn. Rather than being a tool for presenting our "business personas" it appears more geared to being an organisational persona for smaller businesses.
It's only in Beta, so the networking features are rather rudimentary and until the number of participants increases it's not clear how useful they will be. And personally, I'm not sure that this will be enough for Facebook to take on LinkedIn. I think they are going to have to take on board the fact that we all have more than one persona (the usual example is business vs personal) and if they want to be a site that contains both, they have to give people a way to present both sides. This seems to do so, a little bit, for those of us who own smaller organisations, but I'm not sure quite what it does for those who work, say, for IBM. By contrast, LinkedIn at least has some potential there (along with a growing userbase.)
Of course, this could be an example of one of those "enabling technologies" that helps smaller businesses create "virtual organisations" or "network businesses" to cover market requirements that are normally served by much larger organisations. However, there doesn't seem to be enough interactivity to really be better than a phone directory so far. Also, the address form assumes you are in the USA.
This is a pet peeve of mine, but so many "Web 2.0" sites hobble their functionality by not considering non-US users when they first start up. If you're looking for early adopters, it's best to cast the net wider. Ignoring the world outside the US might save 10 minutes coding up the HTML for location, phone and address handling, but you lose half the advantage (geo-location neutrality) of a Web App in the first place.