Earlier quoted context omitted.
I've seen a lot of replies to this comment that are missing the point tomasien is trying to make. BTC can actually completely wipe out the need for VISA, MC, etc. as it can serve for the underlying technology for transactions. The only thing stopping this from happening today is illiquidity of the BTC (insert fiat currency) market. Once we see more liquidity, this dream can become a reality.
Transactions are not reversible. This feature is important. No, BTC cannot replace Visa/MC etc.
How do you think merchants are paid by VISA? Through wire transfers. Are wire transfers reversible? Nope. Yet VISA is a reversible payment system built on top of bank-to-bank wire transfers. Customers deposit funds into their bank account, they get a credit card tied to this account, they pay a merchant with this credit card, the merchant receives the money into their bank account.
Just because the lowest layer is not reversible, does not mean reversibility cannot be built on top. In fact, it's preferable that the lowest layer be irreversible, because irreversibility cannot be built on top of a reversible system.
Bitcoin is the IP Protocol of payment protocols. I'm sure that companies are busy building the TCP/IP protocl of payment protocols on top of Bitcoin right now.