In retrospect, it was an over-estimation by several order of magnitude (my bad) that was promptly corrected by MikeDoug using another data point AWS revenue. MikeDoug estimated (comment excerpts below) the data stored to be in 20PB (petabyte) range, way short of my estimates and may be more closer to reality.
No, doubt, it is still a significantly large number for a service that is only few years old. But, S3 growing up fast may not be as obvious from growth in stored objects as Vogels would like us to believe.
A recent report puts ALL of AWS at the 50 to 70 million in revenue for the year.Other interesting tidbits if S3 has 20PB of stored data, 18 billion objects and 330,000 registered developers:
Let us pretend that, of the 70 million, 40 million in revenue was attributed to S3 alone for last year. That would be $3,333,333 a month for S3. This converts to 22,222,222 gigabytes, or 0.02 exabytes.
On average, each object is only storing about a megabyte of data. This number seems quite low so either deleted objects are being included in the published number of objects or developers are keeping object size low to prevent transfer timeouts.
On average, each developer is only storing 54GB of data. Considering some services like SmugMug are storing terabytes of data on S3, most probably there are lot of registered developers either not using S3 actively for storing data or have services under development.