I think, overall, the airlines are streamlining the whole thing. I used to fly rarely, and frequently have opportunities to be bumped. Now, I fly frequently and rarely have opportunities to be bumped. Even during the 2008 holiday disaster weather in Seattle when one would think they would have overbooked flights to accommmodate stranded passengers, none of my 4 flights were offering any bumps.

Seems to me that AS is putting most of their effort into getting every flight as full as possible, but minimizing oversold/bump situations. This should really help the bottom line...especially since they are offering lower compensation for those volunteers. I suspect their theory is that if it's infrequent, and only a few volunteers needed, they are likely to find volunteers to take less compensation.

My total speculation says that if they do get into a situation where they can either do an IDB, or take an out of town pax volunteer and give them a hotel room, they will choose the latter, and I'd dare to bet that at least the lead has the latitude to do that...after all, IDB's get recorded in a whole other set of statistics that reflect negatively on the airline's reputation...a hotel voucher at a super discounted contracted rate barely makes a dent in the books!

As for being unable to select a seat...I'd still doubt this correlates with the flight being oversold very well...and would venture to bet that you won't even be offered a bump. As MVPG, I have been unabe to select seats on a flight before (and premium seating is available to me). Remember that quite a few seats are reserved for airport control (to accommodate families, etc). Once those are opened up, a few more seats are likely to be available at check in.