About a week ago there were 1.4 billion tweets and 27 million registered users, based on the tweet and user IDs. If anything, that number is slightly more than

About a week ago there were 1.4 billion tweets and 27 million registered users, based on the tweet and user IDs. If anything, that number is slightly more than the real thing, because of deleted tweets and spam. I multiplied the tweets by 200 bytes (I added 40 bytes of metadata, and a 20 byte premium for any unicode tweets). The size of the social graph is harder to estimate. Out of a sample of 459,000 "more influential" Twitter users, the average user follows 262 other twitterers. So the information in the social graph is about 30 GB, assuming 64-bit IDs. They potentially store an edges table of the form (user1_id,user2_id) (60GB), and a denormalized list of followers and friends for each user (30GB each). This comes to about 120GB (I revise my earlier number). Yes, it's a very rough estimation, but it is in the right ballpark.