Good postmortem from the folks over at The Verge:

http://www.theverge.com/2012/6/5/3062611/palm-webos-hp-inside-story-pre-postmortem

Lots of bad timing seemed to kill it. I was previously unaware of all the talent they managed to have under their roof. WebOS really could have been a significant and good alternative in the current smartphone market had a few key things gone differently.