Email is pretty screwed when Gmail goes down, but we don't get a bunch of people talking about how centralized email really is. There's a difference between "influence" and "control".
Well that's because even the Great Gmail has not yet reached the point of being "EMail Central". I have a GMail account but I also have at least 3 other email accounts.
I don't do Bitcoin though so I guess the big question is whether a service like MtGox is actually reasonably necessary or not. It sounds like what MtGox has above and beyond GMail is the built-in network effect that has propped other exchanges up throughout history; you go there to trade because that's where the traders are. You don't have to go to GMail to exchange electronic mail.
I am very fortunate to have cashed out at the peak of this bubble. It's a damn shame mtgox is having these problems. I consider it to be a huge vulnerability of the system.
That said, many people are working on alternatives. It's a growing pain. I need to do more research but the concept behind this project looks very promising: https://github.com/macourtney/Dark-Exchange
Interesting but it looks pretty useless until they can figure out a solution to spam trades (people accepting their own fake trades and impacting the value of the currency), something that doesn't exist yet for now unfortunately, as they admit https://github.com/macourtney/Dark-Exchange/wiki/FAQ
Mt.Gox has became that controlling central without consent from even itself.