When setting up a site, I find all getting into the host, setting up a database, and all that a drag. Instead of using each hosts database, would it be smart to to just connect to one host's database and use the tables on there.. Or would this cause a slow server?
It just depends on what data is being submitted and being retrieved from the database. As long asyou aren't planning on hosting terabytes of accounts on 1 database and pulling it from multiple sites, it should be alright. Just remember, doing this is now eating up bandwidth as the server has to go out of itself to find data rather then staying at "home".
If 500 tables were required... then so be it but theirs a fine line between "Normalizing" tables and Over-Normalizing. Regarding speed though 50,000 rows should be no problem, (if they are indexed, with a pk, and integer datatype on the id field)