So there are now, a few different distributed currencies. Since Bitcoin opened up the field, now anyone can take the open source Bitcoin code, and modify it, and then hey-presto, a new distributed currency. They don't even have to modify existing code, they could just start from scratch!
So if anyone can start a distributed currency, would that not then devalue the existing ones? Probably, however the brains and backing behind the original distibuted currency (Bitcoin), is so good, and the new ones provide so little extra benefit (if at all) that the effect isn't measurable.
I've hunted out the various different types of distributed currency to attempt to explain what the differences are.
|PeerCoin||Proof of stake. Possible Benefits|
|Namecoin||Coins for a DNS system|
|Primecoin||Possible Benefits. Using Prime numbers|