Mt. Gox charging a fee is the same thing as a stock broker charging you a fee when you buy or sell stocks. Mt. gox is a middle man looking to make money....
The beauty of a decentralized currency is that if you think MtGox is too expensive, you are free to perform deals without the middle man. I can buy and sell Bitcoins to my family and friends, with no fee whatsoever.
The bid/ask spread is a little high right now, but the .65% transaction fee seems pretty cheap. But as zillions of Bitcoins change hands, if that .65% fee proves to be too expensive, then someone will step in and offer a competing service for half the price.
FYI, the 30 day transaction history shows that $5.7 Million transactions took place. So the Mt Gox owner pocketed $37,000 last MONTH for this valuable service (less costs, of course). Not bad for a side project, and if you are looking to make a few bucks on Bitcoins, set up a competing exchange with half the fees! It can't be that tough!