[zuck9]

They don't use S3 now. That was way long ago.

Source: https://news.ycombinator.com/item?id=8233622

[rootinier]

Sync a file via Dropbox and run lsof -i, and you get something like this: ec2-54-221-232-10.compute-1.amazonaws.com:https

EDIT: it may be that they use EC2 for their infrastructure, but not for actually storing files. But they still use AWS.