For something to go into the Dolphin core it has be open-source, fully downloadable, independent and royalty-free. Facebook APIs won't ever qualify. Also we don't want to stick more than one brand to your bumper with default package that's for sure. So, yes, we are only talking about module, but trying to understand how much attention, if any, a BoonEx-made Facebook module should get.

As for the other in your list.. interesting topic on it's own:

skype - p2p system, specific application, more see more like "plugins" category

twitter - interesting phenomenon, "different" and straightforward approach, but possibly only one-fifth of what Dolphin is supposed to cover. There's a lot more moving space when you build for specific applications.

linkedIn - good one (although I find it a little messy for interaction) and we're looking at it routinely.

google - still largely a failure in anything social, although some other products provide a lot inspiration (Gmail, Android)

blogger - still going strong, but seem to be stagnating at what they're doing, no? We're watching them too, though.