I'm currently about to redesign a database which you could compare with a database for managing a library. Now this solution will not only manage one library, but 100 to 500 of them. Currently, eg. all the data about the inventory (books) is held in one table for all the libraries.
Is it useful to spread this to one table for each library, by eg. giving it an id as a postfix?
If the libraries don't belong together (administrated and used independently) then it may be worth splitting them into different databases.
If you are really managing ALL libraries together then keep them in the same database and even in the same tables.
Of course you have to be careful when sharing tables - if you screw up, data could be exposed to the wrong parties.
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