Duff-Man says...with the release of Lion thru the app store the way Apple is licensing the OS is (obviously) changing. Without seeing the new license agreement (yet) what may be technically possibly may also not jive with the intent of the agreement. Yes, Apple has not been too fussy in the past with OS licensing and piracy but the distinction still needs to be made, as I don't think anyone wants to see some convoluted activation scheme.
If I was to make some kind of guess, I'd say perhaps the agreement mentions something about the "primary user of the computer" or something like that, or at it should....oh yeah!