What the hell is a Tweetup?

I thought I'd take the question above as a starting point. A Tweetup is a new concept and it's something that is really starting to catch-on in some places.
I organised and hosted Preston's first Tweetup just over a week ago and it was a roaring success. We had nearly 40 people in the room, many of them with wireless enabled laptops and mobiles, all contributing to a discussion on one topic.
The idea for a Tweetup is that instead of having a networking event or discussion where the conversation is completely physical you also have a virtual conversation going on. Bear with me, it does make sense. The structure of the event is an opening preamble and then a topic is discussed by the people in the room - often splitting off into separate groups. This makes it easier to manage.
For example, at the Preston Tweetup we were discussing the Preston Guild in 2012 and how the web can be used in it.
The discussions were flowing around the tables but also on twitter, take a look at the #prestontweetup hashtag feed and you can see all the good stuff that was coming out of people chatting about the topic. Yes, some of it went off on tangents - but that happens with any discussions.
The best thing about the Tweetup was that as an organiser I was getting instant feedback. If there was a problem with something I could pick up on it straight away by watching the tweets. I could also easily collect information after the event and condense it.
This backchannel conversation was incredibly useful and exciting. It also allowed some great interaction between the groups, so that people might take a question asked by one group and explore it and the then fling some more questions back out into the twitter stream for other groups to consider. There was a fantastic collaborative environment at the event.
So, I would really suggest giving a Tweetup a try. You don't need 40 people there, maybe just 5, but get going with it and see what happens. And if you're in the education or conference/networking sectors, you need to be on this. Doing it. Making it happen.