There were already exchanges before Mt. Gox came into the picture, centralized exchanges. But, of course, the Bitcoin community at that time was small and close-knit. They probably knew each other and linked to each other in one way or another. So, at the start, it was purely peer to peer exchanges. Also, it was much easier to mine Bitcoin yourself. You don't need to have a powerful ASIC to be able to mine. So you can get fresh Bitcoin yourself.


There was also Bitcoinexchange.com, the platform developed by Martti Malmi, Sirius here. Sirius made the announcement about it on March 02, 2010. Satoshi supported the exchange himself/herself/themselves, and somehow even made sure that there's actually available fiat in case somebody wants to sell.