It occurs to me that once one crypto-currency (bitcoin or what have you) really begins to break through, it would be a small matter for large corporates to put their own out there -- or coop the existing one by paying a small price by corporate standards. It could also be the case the governments adopt a hybrid model and issue their own crypto-currencies (backed by the nation-state). What stops either of the above two scenarios from happening?
Not much really except more miners getting in on it and securing the network. Paypal is considering it but I reckon they'll make their own so they can enable refunds.