I've changed the way we export user data.

Once every hour we check every user's table to see if they've posted anything in the last hour.

If so, we backup all the data we have for them that isn't already backed up.

This means everything but the posts, which are preserved in the RSS archive structure. Have a look in the microblog namespace for an explanation of how this works.

We used to back up the whole user's table, but that was highly inefficient. Now we backup the prefs, stats and callbacks for the user and for each feed. The calendars are not exported. That's what grows.

This is my exported data file.