[mikeash]

The idea that the hosting would get cheaper over time is interesting. If you assume that the ongoing costs follow a Moore's Law type exponential curve (which may not be true, but seems like a decent rough approximation) then the total cost to provide a constant service for an infinite time is finite!

[TillE]

Computation will always require some energy though, so the cost will approach some nonzero constant. Still infinite.

http://en.wikipedia.org/wiki/Landauer%27s_principle