I’ve been asking people involved what went wrong and two common themes have evolved:
1. Their bet on Microsoft technology doomed them for a variety of reasons.
2. Their bet on Los Angeles accentuated the problems with betting on Microsoft.
Nice assessment by Scoble, who believes that talent location and technology debt are the root causes of MySpace's failure. What decisions have you made that are limiting your opportunities for growth.
One "persona" that many product managers miss in their planning is "the system." Sometimes we have to do things to improve the health of the architecture or make it easier to build on. It drives sales people and execs crazy because features for "the system" don't demo... but, like a healthy work-out at the gym, you do it because it's good for you in the long-term.