Exchange 2007 gave us a maximum of 50 storage groups and 50 databases. Exchange 2010 allows us to have a maximum of 150 databases mounted at the same time on a single server and storage groups have been removed. Although each server can have only 150 databases mounted at a given time, this limit does not apply for the number of database objects in AD.
An exchange 2010 organization can have any number database objects!
