This has been forwarded before and I agree with detractors to this kind of thinking.
First, HP is a big company that has much better ways to turn money into more money than making something people are unwilling to buy at a reasonable price.
Second, growing the webOS ecosystem in this way founds it on false principles. Everything that seems to work when you're selling for a loss, might not work at all when you're selling for a profit. Just imagine if HP started off selling a $99 TouchPad, blowing out the doors, piling up billions in debt, and then found out everyone wanted an iPad when the price went up to $500. Oops.
The best modern example of this I think is Groupon. Groupon has been growing like crazy by taking a huge loss. For every dollar it takes, two dollars go out the door in the form of advertising and client acquisition.
Groupon is already of questionable value to some businesses. When the time comes for Groupon to fix its profitability the value proposition may be lost entirely.