When will virtual currencies be useful?

I currently have small amounts of money floating around in a variety of virtual currencies. In some cases, I can convert those currencies to other virtual currencies or to real world money (i.e. there’s a slow process to move paypal money into my bank account).

It occurs to me though that it would be very useful if I could pay real world bills (think groceries or mortgage) directly using virtual currency.

Before that can happen, there would need to be a lot more transparency (i.e. no grocery will accept magicbuxx if they don’t know how much they are worth, or whether they can in turn get value out of them), and a whole lot of big institutions like banks and payment portals would need to sign on too. There would also need to be physical mechanisms that can transfer the payments (i.e. the new mobile payment technology that is slowly being adopted by cellphone manufacturers would be helpful).

I wonder how we can make that happen. It would be very nice to be able to go to a restaurant with a pile of Facebook credits, or Bitcoins.