in private message: also match last names in auto-complete of To-field I am using the private message module and I do understand that one can use realname integration in the "To"-field to send a message. The auto complete feature helps finding the name. 

Suppose I want to write to "John Smith". When I start typing "Jo.." it auto completes to "John Smith", but when I start typing "Smi.." auto completion fails. For my website it would be very nice to have that feature, since sometimes people don't know other peoples first names, but the last names. 

How could I alter private message in the easiest way? Do you think other people would be interested in a more comprehensive auto completion?
There is an issue in the Privatemsg queue with an incomplete patch, privatemsg_realname: Permits to search inside realname field using "LIKE %...%".  You're welcome to help re-roll and test the patch.

The patch is for 6.x-2.x but it could fairly easily be re-written for 7.x-2.x.