It looks like almost every cloud provider hide their numbers, which makes guidance and education unnecesserily difficult. To be fair, I think I saw AWS posting a few items for S3, but forgot to save it. So, I'm going to preserve what one Chinese gentleman posted to OpenStack list, in the context of Swift performance issues:
Our practice of Sina Web Service Team https://launchpad.net/~sws: total accounts: 121,961; total containers: 160,703; total objects: 14,291,519; total storage usage: 1.3T account replication time: 10 hours; container replication time: 10 hours; object replication time: 48 hours; account audit time: 2 hours; container audit time: 9 hours; container update time: 19 hours;
Unfortunately he omitted the requests per second and gigabytes per second that the cluster is sustaining from the users, but it's very interesting anyway.
QUICKIE: Apparently I meant the official post about Amazon S3:
total objects: 905,000,000,000 total bytes: ? requests/s: 650,000
UPDATE 2012-06-12: Amazon announced that they reached a trillion:
total objects: 1,000,000,000,000 total bytes: ? requests/s: 650,000
The growth rate, according to my calculations, is 18,325 objects/s. The blog article claims 40,000 objects/s.