For some reason, everyone wants a tablet. Few know why. This article looks into that.
http://www.engadget.com/2011/08/21/editorial-tablets-arent-the-third-device-id-hoped-for-fr/
Why would you buy a $99 HP tablet when it will no longer be supported? Lots of reasons. First, it will be supported, directly or indirectly. WebOS is not new. It has been around longer than Android and is well tested on the phone side. It was developed at Palm before being sold to HP, so the basics are solid. HP hasn't said WebOS is going away, in fact have gone out of their way to say the opposite. They hope to license WebOS to others, or continue to enhance it themselves. What they are getting rid of is their tablet hardware, and hopefully the personal computer division. It may just be PR speak, but for now WebOS isn't dead, and even without HP it will likely continue to be "supported" by others.
Is the tablet perfect? Nope. The hardware is a bit too slow. But as long as you are buying it knowing what it can and can't do, even if HP disappeared tomorrow the device wouldn't stop working. When people bought a Playstation years ago did you worry, oh no, it can't be updated over the internet it won't work? No. My original Playstation still works.
The device will play music, browse the internet, and play videos. That functionality is no less solid than similar devices. Maybe in 3 years a new internet technology will come along that this won't support, but for now it supports HTML 5 and flash, something even the iPad can't say.
Finally, this is a $309 device. That is the actual raw material cost. This isn't a generic off brand MP3 player, it is a solid device with the occasional hiccup any other tablet also has. Look at online reviews. People were happy with their purchase at $399, to get the same device at $99 is unheard of. That is why everyone wants one. At $600 an iPad isn't an impulse purchase. At $99, I'll gladly upgrade my daily train commute video experience from phone to 10" tablet.