Locking down the people picker to an OU

I thought I'd already covered this, but a quick look through my history shows I didn't.

Locking down a Web Application's people picker to a specific OU is very easy, but not well known.

stsadm -o setsiteuseraccountdirectorypath -url http://WEBAPPLICATIONURL -path "OU=OU,DC=DOMAIN,DC=COM"

Its really that simple, just point the path to the distinguished name of your OU, and you're set!