I've been looking at various social media plugins out there, some specifically to each network, some all-in-ones. Problem with picking the specific ones are that they don't work together and I'd prefer not to have a mess of plugins in my installation. For the all-in-ones, they're resource hogs.
Why doesn't WPMU put one out? Keep the integration to the major networks like Facebook, LinkedIn, Twitter, Google+, etc. Furthermore, an elegant solution like Yoast's (http://yoast.com/social-buttons/), but in the form of a MU-compatible plugin, would be ideal.
I think this is one plugin that's sorely missing from WPMU's excellent library. I hope you guys consider developing one.
But, until then, I'd appreciate some suggestions.