I should note, that one of the reasons the database is so large is that we keep two copies of each post. One the already marked up version (all ubbcode converted) and one of the original post, for editing purposes.
For version 8 we'll be introducing an archive feature, so you can archive older posts. When posts are archived, we will no longer keep the original post, only the marked up one. So those people that have a lot of older posts can choose to archive those, which will free up quite a bit of space.
