Wikipedia, under Blu-ray Region Codes:
In circumvention of region coding restrictions, stand-alone Blu-ray Disc players are sometimes modified by third parties to allow for playback of Blu-ray Discs (and DVDs) with any region code. Instructions ('hacks') describing how to reset the Blu-ray region counter of computer player applications to make them multi-region indefinitely are also regularly posted to video enthusiast websites and forums. Unlike DVD region codes, Blu-ray region codes are verified only by the player software, not by the optical drive's firmware.
The last sentence is particularly interesting and would be even more so if I knew what it meant.