Multi DB hosting isn't the issue, it's installing two MySql server instances that I think people are questioning. I know with MSSQL there were scenarios where

Multi DB hosting isn't the issue, it's installing two MySql server instances that I think people are questioning. I know with MSSQL there were scenarios where you would install multiple instances, I think they were when you had more RAM in the box than the server package was licenced for, or for management of a large number of databases.