A nice infographic from Webtrends which looks at how the Royal Wedding was discussed in social media. I'd say they're massively under-reporting the conversation on Facebook (probably as it isn't visible to their tool):

The Royal Wedding social media snapshot

Twitter's media blog also has an interesting round-up of how broadcasters integrated Twitter into their coverage of the wedding.

Update: The official Royal Wedding website has released some impressive stats on their YouTube, Facebook, Twitter and Flickr presences.