A billion streamed videos per day, $0 in bandwidth costs

Google recently told us that they have reached the one billion videos per day mark, but are still quite tight lipped over the actual cost of the service. It's hard to imagine that streaming a billion videos per day would be cheap -- but in Google's case, some say that it might actually be closer to free.

How is this possible? Years ago, Google bought up a bunch of dark fiber -- which cost a lot of money at the time. Turns out that it was basically a one-time investment that is the key to making YouTube success viable. Of course the hardware that supports the fiber isn't cheap -- and is still subject to maintenance which isn't free.

Google is basically in a position with this service now where traffic is an asset, not a liability like with most other sites that deal with streaming video. Let's hear what you think. Can Google's bandwidth costs for YouTube actually be free?