The incentives also don't line up on the buy side. As a buy-side fixed income investor, you can buy a 10-yr US Treasury (AAA) yielding X%, or you can buy a slice of the 10-yr AAA tranche of the Abacus CDO yielding X+0.50% (made-up but representative numbers). You're suspicious of the long-term performance of Abacus (it's 2007 and you're already hearing rumblings about problems in the housing market) but your bonus is based on the quarterly performance of your portfolio. It's pretty clear what most institutional investors did in this scenario.
