A Sony representative answered a few quick questions to GameSpot about the DRM on the downloadable edition of Warhawk.
GameSpot: What's different about Warhawk's DRM?
Sony representative: The downloadable version of Warhawk, which is available from the PlayStation Store, will be directly tied to the registered PSN account that purchased the game. Only that registered PSN account will be authenticated for gameplay. You will still be able to download the game to up to five PS3 systems. However, if a user downloads Warhawk onto a different machine, he/she will only be able to play via the original PSN user account on that machine and could not play on a different machine for 24 hours. This does not affect the Blu-ray Disc version of the game available at retail.