Does ALLOW SNAPSHOT ISOLATION need to be set on Tempdb itself?

I'm in a debate over whether you also need to set ALLOW SNAPSHOT ISOLATION on *tempdb* itself, or only on user databases for the functionality to kick in (in addition to code referencing this)? Most articles and examples seems to set the property on the user database itself only and leave *tempdb* to OFF as is. But then I found this one link Pro SQL Server 2005 Database Design and Optimization , which says: >(You can even do this on tempdb) alter database tempdb set allow_snapshot_isolation on Is it necessary to also set it on *tempdb* in addition to the user database, or just the user database? The main purpose is for an application that needs to have snapshot isolation on.