Just doing some reading and found that there exists an 10 database limit for DB mirroring on SQL 2005/2008 32 bit version.
We have a 2005 32bit SQL server that is currently mirroring close to 30 databases with no problems. When I try to add one more i get Out of Memory errors which prompted me to do some research and find this limitation.
Do the 64 bit versions have any limit? This might be a good question for the QOD. 🙂