The only piece of hard data I've seen was what MagicalTux said on July 21st: "We got in June a total of $6,824,168.53 of funds moving around (16640 transactions in both deposits and withdraws) over Dwolla, equivalent of $227,472.28 per day, or $1,592,305.99 per week"
Roughly, that means that if mtgox has 500k btc on the site (I think he demonstrated he had control over a wallet with almost 500k coins), and if the amount of funds now in their bank account is still around $3.5M (the same as it was back then), then coins should be priced somewhere around $7. I know this isn't a reliable or convincing data point, but it's the only data point I've ever seen concerning btc fundamentals.
I think what has happened lately on the sell side, too, is that those miners who were previously selling and extracting via one Dwolla account with MtGox finally realized they could sign up everyone in their immediate and extended family to get around the stupid $1k withdrawl limit. Tradehill should, because they lack a reasonably cheap way for buyers to get money in, always run at a lower buy/ask than MtGox.
Whenever I put up a bid anymore the price moves to that range quickly. This does seem to be happening on the large sell side too occasionally, however, which makes me think this is simply a bot using its existing coin to manipulate the price.