When you are constantly editing and formatting a post in WordPress 3.0.1 it will “auto save” and the list can long. One of the disadvantages is that the data base may grow and if your database is been hosted by third part company (like mine) you will get to its limitation allowed very quickly.
It is also made sense to delete and remove all existing stored post revisions and changes made on pages stored in the database in order to reduce the wp_posts table size, especially when there is already tons of revisions or changes been kept.
To delete and remove all existing post revisions entries and rows from WordPress database Posts table, simply login to MySQL command-line using phpMyAdmin, MySQL GUI tools, or other MYSQL Tools take a backup of the database first and run the following command.
DELETE FROM wp_posts WHERE post_type = "revision";
Here is an image of my execute command: