Actually, if you want to move files across disks, you use command-drag to force a move rather than a copy. There is no way to force a move when you are copying across owners.

Command drag worked for files but not folders. And changing the permissions had no effect.

Command-drag works for folders for me (10.6.4). What version are you on?

It's not like this is a recent feature. The option/command modifiers for explicitly copying or moving (respectively) have been around since at least System 7.

yeah, that happens to me all the time. just this morning I "discovered" that you could use Expose to flip through windows application by application by hitting the tab/shift-tab keys while in Expose mode (a feature introduced in 10.3, so I learned). I still thought it was exciting, though. :)