HP's management has been completely braindead for the better part of a decade so their leaving the consumer PC biz shouldn't be taken as a sign of anything beyond their own incompetence.
Yeah, the idea that what just happened at HP is indicative of anything in either the PC or tablet space is just not valid. Aside from HP's own long standing problems, Palm itself has been passed around like a hot potato for a long time now.
Even people crediting their failure to Apple rings hollow. The Touchpad is inferior in terms of hardware to a LOT of tablets, it was clearly poorly managed and was released at a price point that simply wasn't viable. This was HP falling over itself, pure and simple. They didn't need any help from anyone else.