If you haven't been following all  the  conversation  around  MPI WEC and the  socia media gurus , you should. At least if you have any interest in trying to figure out how to work with bloggers, tweeters, and the rest of the social media gang who most likely will be coming to your next event.
I'm not sure if I would go with a formal program like MPI did with its SMGs, but I do like the idea of offering registration discounts or some other type of perk to attract the twitterati who may not otherwise come. The first thing to do, though, is to know what you want from the social media elite when it comes to your meeting.
• If you want them to promote your event pre-show, or certain aspects of the event while it's happening, I don't know as how you need to do much of anything. I'd ask my organization's staff to put whatever it is we want to promote out there and trust that people will retweet if it's interesting. If it isn't, it'll fall on deaf ears no matter who puts it out there, IMHO.
• If you want to give those who haven't used social media a taste of Twittery fun, having a few volunteers stationed in the Hub with a big screen of the latest mentions on LinkedIn, FB, Twitter, blogs, etc., and a computer to show people how to get started would probably be welcomed. Those of us who've been using all these media channels for a while tend to forget that getting started can be intimidating, and a friendly face to guide the set up would be a nice service to provide.
• If you want to engage and excite SM-active members, I think a simple invitation to join in the discussion and what hashtag to use would suffice. Everyone who wants to join in will anyway, from my experience. One thing that I saw at MPI WEC that was incredibly cool was that some of the speakers were sending tweets to the #wec10 hashtag, and it was obvious that they were paying attention to what others were tweeting about, too.
ASAE also has done a terrific job over the past several years in involving members/attendees in its social media efforts. They invite certain people to post right to the Acronym  blog, and are fantastic and providing pointers to any and all posts they can find about their meetings. Last year's social media hub -- which incorporated meeting-related tweets, blog posts, you name its all in one place on their Web site -- was a thing of beauty indeed. They have a lot of members who are very active both with the association and with social media, and it looks like they are ready, willing, and able to jump in and lend a hand as needed. I wrote a bit about ASAE's media strategy  after last year's annual convention, and I bet they've done a bunch more since then.
While all the industry associations are giving it their best shot, so far I think ASAE has the best handle on using social media to support its conferences. But ASAE, like MPI, PCMA, other industry organizations, and the rest of us, are still trying to find better ways to make social media enhance, not distract or detract from, our shows. If you have any interesting ideas, I'd love to hear 'em.