This afternoon I came across one of the "ridiculously low" rates at the Anchorage Marriott Downtown for next summer. Clearly the decimal point was in the wrong place. I booked online, and then quickly called the hotel and asked to speak to the manager. The response to my inquiry on whether the rate would be honored was an emphatic "ABSOLUTELY NOT, we can't give away rooms like that!" I told him that he could go ahead and cancel the reservation and I would rebook with points. It was worth a shot!

Bonus Bucks are used as promotional material for lots of things (from time to time). For instance, a couple years ago (2002) for a while you could buy a $50 Marriott Gift Card (for $50) and they would throw in a $25 Bonus Buck certificate. I've also heard of them being used as a rebate/reward for certain IT purchases (I think it was HP printers) where you would get three $100 BB certificates with the purchase.

There may be more. Keep your eye out (and check this forum regularly).

BTW, there are sometimes more than one OTP rate offered for a given property. Recently I had booked an OTP stay at a particular Marriott at $159 per night, and checking back a week later found an (apparently) identical offering under OTP for the same property at $129 per night. Needless to say, I cancelled the initial reservation after rebooking under the lower rate.