Speaking of notorious, every transistor in every chip has a range of voltages that it recognizes as zero, a range it recognizes as one, and a band of voltages in between which it might interpret either way or not at all. Brownouts cause power supply voltages to fall in unpredictable and probably unrepeatable ways. When power supply voltages fall, all voltages in a chippified device (computer, PDA, set-top-box) fall. If there is enough power supply voltage to make the chips operate at all, and their input voltages jump around where they should not be, all hell can break loose. It would NOT be farting around to put a UPS on every product in the house that has a microprocessor!