[rchowe]

Remember that as time goes on drive space prices fall as well. If you build backblaze storage pods[1] a petabyte over 3 years costs you a little under 100k. If we assume the average email user uses around half a gigabyte[2], we can accommodate around 2.1 million accounts on the petabyte (more if you compress the data). Throw in another two petabytes for compressed backups and you've got a million email accounts for 150k, or $0.15 an account (over three years). If you show users ads that average more than 15 cents per user over the course of three years you're making money (less paying employees that don't operate the storage, etc.). The actual numbers may even be less. Combined with the fact that the price of storage seems to still be going down at a rate that most likely is faster than user inbox growth, and you'll never hit this particular singularity.

[1] http://blog.backblaze.com/2011/07/20/petabytes-on-a-budget-v...

[2] 200MB more than the amount currently in my gmail; I have email going back six years and I never delete emails, but I'm not a heavy email user.

EDIT: Formatting