two things...

all exchanges are essentially "meetup" groups, that is how the first exchanges/bourses/markets started. Whether people "meetup" online, or in person, you are joining a group for the purpose of transacting. Also, I think that you are mistaking differences in scale to differences in kind. A market is a market, whether it is a large market, or a small one. The goals and methods are the same. That is also why Satoshi Square is not the same as other meetup groups, people are coming prepared to trade (cash and bitcoins), because they know the goals of the meetup group they are attending. If I show up at a meetup group that is based on providing information, and ask to buy (or sell) $10,000 worth of bitcoin, I most likely won't be able to do that, the people who can facilitate transactions of that size may not be present, or may not be prepared. Like all meetup groups, clarity of focus and stated goals is what is important. There is no reason that you can't have multi-dimensional meetup groups, and that is actually how I see this idea spreading to multiple days of the week.

Second, the guy who bought $10,000 in one shot was not providing liquidity, he was taking liquidity. If you understand markets, you will know that this is the case. We typically have many people willing to sell, if the price is right, but they are basically leaving orders on the book, he came in and did a "market buy", and swept through the book. We were able to provide liquidity for someone who wanted to execute a large trade, he had not arranged this trade in advance, or planned it out with others, he just showed up, and expected that people would be there to fill his order, and they were. You can also tell who is the maker and who is the taker by who set the price... Providing liquidity is the service of satoshi square.

I think there was some talk of starting one in San Jose/San Fran/Bay Area, but I am not 100% sure how that is coming along.