Flooz is no counterexample. Durability and limited supply was guaranteed by single company which is not a guarantee since companies are born to die most of the time.

If you'd mentioned Flooz as counterexample to the claim that WoW gold has bright future as currency and store of value then I'd wholeheartedly agree.

MtGox is just biggest place where people trade bitcoins but there are many alternative markets. Talented developer can set up new market within few months. Of course fall of MtGox would anger and put off many people but end of MtGox is not the end of bitcoin.

Price speculation and money laundering increase value of bitcoin which attracts more investors to it and draws public interest to bitcoin. Purchasing illegal goods with bitcoin is also good because it provides immediate utility as more and more things nowadays are illegal.

> if bitcoin is mainly used to buy drugs, guns, and child pornography, then I don't really want to use it to buy dinner

Does financing manufacturing of military grade weapons that are constantly used to kill lots of people not bother you? Does financing dictatorships by purchasing of their oil with dollars not bother you? Does participating in global casino where whole banks play (calling it "investment") that artificially raises cost of such basic things as food for millions of impoverished people not bother you over your dinner bought with dollars? I think this last thing is what dollars are "mainly" used for nowadays.