I installed a forum, and forget about it. After several months, I received a Mysql Quota warning, and found that the forum has got thousands of registered users and posts. All of those usernames are randomly generated and posts are ads with many links, fortunately there are no adult photos and videos. Here is the Mysql Quata warning email: Dear Valued Customer We are mailing you to let you know your free account has exceeded its mysql quota of 50mb. The ability for your user to add new data to your databases has been revoked (denied) due to the quota breach. You will be able to log into phpmyadmin (or possibly use tools in your script) to remove data from mysql. If you are unable to reduce your database usage to under 50mb, we would ask you to upgrade. Best Regards Besides of the restriction of SQL usage, there are disk usage quota, bandwidth usage quota and daily CPU usage quota.