mySQL - Am I thinking right?

Hi

I am planning a BIG app. When I say big I mean it is for not least then 400 000 clients. Each client will add info to the database, and I thought that, it is to much for one table alone.

I thought that the script should generate a table for each registration and each database should hold no more then 5000 tables. So each 5000 will be created inside a new database.

Am I thinking right? How do the FaceBook work?

Am not creating a new facebook, is a tool for teachers but the concept is the same.