I talked about this in a separate thread. The p2p part is really important, but it can't interface with non-p2p stuff like regulated corporations. It also doesn't really have to.
A currency exchange addresses two problems:
1. Coordinating the market price of the currency pair.
2. Safely transferring ownership of the traded currencies.
The first problem can be solved completely within a p2p system using only bitcoins as the currency. See Prediction Markets.
The second problem is tricky because it involves transferring ownership of fiat money, e.g. USD. But, if the market price is known to all via (1), it becomes a lot easier to just meet somebody on the street and swap dollar bills for bitcoins, or do it via #bitcoin-otc. So I think the hard problem here is the prediction market.
1. Coordinating the market price of the currency pair.
2. Safely transferring ownership of the traded currencies.
The first problem can be solved completely within a p2p system using only bitcoins as the currency. See Prediction Markets.
The second problem is tricky because it involves transferring ownership of fiat money, e.g. USD. But, if the market price is known to all via (1), it becomes a lot easier to just meet somebody on the street and swap dollar bills for bitcoins, or do it via #bitcoin-otc. So I think the hard problem here is the prediction market.
I agree. The cash in hand for Bitcoin amount would have to be negotiated up front.
I did find 3 places (In the Wiki) currently doing this:
http://btcnearme.com/
https://ubitex.org/
http://tradebitcoin.com/about
