never seen information like this, don't take me wrong but this can be limitless if you have proper resources. But take it like this, your size of database is either limited by storage capacity of you pc/network or your webservice provider
I agree, I think you will run into hardware limitations probably long before you run into software ones. Plus, I don't think there is a size limitation on the database so much as on a specific table. I believe the major DBMS all boast being able to handle 2TB size tables.