once you require a central service, you're vulnerable to government intervention and you'll suffer the same fate as egold et al. heck, if you want to rely on something central, you could run the transaction database centrally as well and leave out all that mining stuff.

the only thing to ponder is that it's true that anonymity (as in no id necessary) is not required for a currency to save world economy. but as long as governments are not interested in saving the world economy, it has to be done by a digital grassroots movement like bitcoin, which demands for anonymity simply because there can't be a central authority to verify identities.