It looks like MtGox only displays a fee when I bought BTC... When I do the calculation for selling BTC, though, I am charged the .6% fee then as well. That seems kinda shady, if you ask me.
Also, if I trade BTC-->USD-->EUR-->BTC am I charged the .2% fee three times?
All exchanges charge transaction fees, that's the source of their income. I don't know the specific fee structure for MtGox.