Would it matter?

I am almost completed another PHP forum script which I am trying to setup a dedicated forum hosting site. Currently, I don't have the money to get a dedicated server, so I'm using webaxxs.net which is offering me only 4 db to work with. So here's my question . . . Would it matter to the server if I decided to host forums on one MySQL db? I have 13 tables and I could write the managing script to prepend a username to each 13 table to make them unique and won't conflict with other tables in the db. Would this serverely create some problems for the SQL server in the long run? The only problem is that there will be alot of tables in one db and can get a bit confusing. Is there any other problems I would face? The other way I could go is host each forum with it's own seperate db. That would mean I would have to find someone to partner up with and see if I could cut costs and split a dedicated hosting service. Is there any benefits to this other than a more organized way?