If you haven't already, go read TheVerge's excellent piece on WebOS. Lots of interesting details there.
http://www.theverge.com/2012/6/5/3062611/palm-webos-hp-insid...
http://www.nytimes.com/2012/01/02/technology/hewlett-packard...
The primary issue with webOS, according to Paul Mercer, was that it "was ahead of its time in trying to build a phone software platform using Web technology, and we just weren’t able to execute such an ambitious and breakthrough design."
It's intriguing to note that tomorrow RIM will officially unveil BB10 and its first line of BB10 handsets — another phone software platform built using Web technology that is, in many respects, the heir of webOS.
The multibillion dollar question: has web technology finally reached the point that a phone platform built using it can be executed successfully head-to-head with iOS and Android?