Regards to the deliberate bumping strategy it is quite difficult to actually pull off. Suppose you buy an unrestricted, refundable ticket, then two possibilities arise:

(1) you get a boarding pass and then they ask for volunteers and you get bumped. However if the flight *isn't* full you have to back out at the last minute and get them to cancel your boarding pass and then refund your ticket. Difficult to do without drawing suspicion to yourself.

(2) you don't actually get a boarding pass but just go directly to the departure gate (possible in US airports only) - in which case by the probable time they are looking for volunteers (about 5-10 min before the flight) they are likely to deny giving you a boarding pass on the grounds that you arrived too late to get one and hence aren't entitled to being compensated for being bumped.

I admit that the above problems aren't unsolvable but do make it punitively difficult. If someone has a solution or critique of my analysis, please email me privately (I'd be happy to oblige the favor in any way I can - computer programming, upgrade coupons whatever !)