I installed the UpPrev Plugin for a very short period of time on a website with 13,500 posts. After removing the plug my site crashed. Upon several hours of investigation I realized with the help of Rackspace support that the program had created 121,300 entries in my WP-Options database after the plugin had been removed.
Had to use a SQL Search to find the records and then run a query to delete all of them as the program was depleting all connections via Rackspace Sites.
This problem was verified by me and by Rackspace support.