Unless the readers, computers, OS, etc... will still be in use in a billion years, this is not very useful.

If MS gives the xbox cable hosting capabilities, and partners with a cable provider like Comcast so that they offer the Xbox as the rent-a-cable-box solution, they would make an absolute killing.

Agreed. This calculation is more useful for local attacks (e.g. - pwd protected archives, encrypted file systems, etc...). Attempting a brute-force hack of any online account or system would be silly, as any system worth their salt would stop the attacker after a few tries and raise red flags.