Just read the blog about the servers being slow,
Save some space and cull some users.
2005 - 2006: 1020 users with 0 posts
2005 - 2007: 1620 "
2005 - 2012: 25078 "
Removing all users with zero posts that signed up before 2008 - 2009 is a safe bet these people aren't coming back, have lost their pass, have a new user name.
By banning/monitoring things in names like 'pharmacy', 'Viagra' and other associated words, spam/bot users might be prevented.
User files can be hashed periodically to combine like uploads, I bet there are doubles, even triplets of many documents in the file sump.
Might not seem so big now, but with 50 average new users a day ( was 40 like a month ago ), there will be an exponential growth in unneeded data in the next 7 years.