Money stuck in exchanges keeps the Bitcoin price artificially high. If Mt.Gox ever processes all withdrawals, more people will convert to fiat to get their money out. So prepare for a price drop when they do.
It might also increase trust in bitcoin and the ecosystem, which could lead to another run-up.
Mt. Gox is almost irrelevant to Bitcoin at this point. Since they're not paying out USD (at all) or EUR (much), and only an idiot would deposit there, most of the "volume" there has to be the same money sloshing back and forth within Mt. Gox.
More than one million USD worth of other currencies (mainly JPY) are leaving MtGox every day, and I assume some people are depositing as well. Otherwise the price would go down, not up. MtGox still has the deepest order book. There are more than 24 million USD worth of bids at MtGox. There were only 12 million USD in bids a few weeks ago.
Most of the volume on most exchanges are the same money trying to buy low and sell high. Probably more so on MtGox due to their superior API which makes them very attractive for bots, but that doesn't make the price invalid. Bots are good. Bots provide liquidity.
Price setting has mostly happened on BTC China the last week or more, with MtGox following closely. The other exchanges lags a bit behind, usually.