My best bumping stories happened when my company transferred me to PHX from LAX. For a month I had to commute to LAX on Monday and PHX on Fridays. The 5 PM, 6PM and 7PM flights were always oversold. I volunteered each time they offered and in that month racked up over $3k in vouchers.
The only drawback, it was with AmericaWest who is probably the worst airline in terms of service and on time record. But free travel is free travel. Also, they are reluctant to transfer remainders of vouchers.
The lesson is to be flexable, friendly and firm when it comes to the carrier breaking their contract with you. Always dress to impress and ask if you can be upgraded to first class. For me it has worked enough times to justify donning the suit and tie.