There's a fixed number of them, 21 million (not all have been created yet). Many online businesses are using them for transactions.
I have just been looking into trading them, I don't own any yet.
Unlike fiat money there is a fixed amount of them so devaluation can't occur, similar to gold / silver though obviously it isn't a physical item.
I've been looking at setting up an account at mtgox.com which trades them.
https://mtgox.com/
I agree though, a physical commodity is always the best to own long term. I don't have full trust in cashless currency and to me it smells a little fishy as in a way to get people into the cashless society.
