There are two problems with that I can think of:
1. Bank transfers can be reversed in some circumstances (account was stolen etc). Some days after Bob gets the money and releases the bitcoins, the bank may reverse the transaction.
2. I'd be worried that the bank may freeze my account if I receive cash transfers from someone who turns out to be a criminal or the bank freaks out for some reason.
I would much prefer a centralized exchange.
This concept could work if A and B meet up and payment is made in cash. This concept could also work for trading between cryptocurrencies (btc <--> ltc etc)
I think these are serious issues which need to be considered
This is the 3rd time these points have been raised - you seem to have addressed literally every other post specifically apart from these ones.These maybe hard questions to answer, but if #2 in particular starts happening for users of your system, you will become a VERY unpopular person, VERY quickly. Having a primary fiat bank account closed or locked is far more damaging and off putting for the novice user (who you've said this system would be for) than losing some fiat or some BTC.
There is no question that this is a huge issue with p2p systems using bank wires. However it seems to me you're missing a critical aspect -
the very fact that the system is P2P rather than client server can lower the chance of an account getting blocked.
If banks start seriously blocking bitcoin-related transfers, they have to have some evidence to suggest which out of the hundreds of thousands of wire transfers a day are related to bitcoin. If all fiat-btc transfers are via one of 10 different exchange companies (especially if they're international), it is not very difficult for banks to do that. If the transfers are peer to peer and local, not so much.
(Of course banks freeze accounts for non-bitcoin reasons, I'm not suggesting the P2P aspect removes the blocking risk, but it moves the goalposts)
I'll take this opportunity to let people know of the architecture I'm working on coding right now - description
here. Read the ssllog thread for more details if you're interested.
This issue would be solved easily if you banked with a crypto-currency friendly bank. "There isn't one" you say, then