A recent Apple technote warns to never, ever fool around with any of the many SyncServices folders or subdirectories.
As if it were a swarm of bees, you should stay away from the SyncServices folder in Mac OS X. Removing or modifying anything in it—or in subfolders within it—may cause unexpected issues. This folder is located in your Application Support folder, in your Library folder, in your Home folder.
The note says that deleting or modifying items in these folders "may cause unexpected results," including data loss or duplicate items in Address Book and iCal.
Of course, SyncServices syncs and you could lose or screw up the same data in your iPhone or iPod or on your .Mac account. "This means data could be lost on other computers," the note warns.