I ask this specifically for SQL Server, the advantages that I can see for multiple databases are:

 1. Logs are smaller (so one runaway transaction cannot cause others (replication etc) to stall)
 2. A page corruption does not affect multiple applications (can this be isolated using filegroups?)

I can't seem to find any benefits from a single database architecture (maybe the code management is simpler).

Which architecture did you choose and why?