It all depends on whether you can afford to replace it if it dies, and how well they actually honor it.
The fact that they make money on every extended warranty sold is obvious, especially considering how much they push the warranties. So if you buy a few million laptops, you're better off just warrantying (is that a word?) them yourself since the percentage that break and the cost to fix them will be less than the warranty cost for all the laptops. The same can go for buying just 1 laptop, but its much more of a gamble. You're betting that your particular laptop won't die on you, and the odds are generally in your favor if you avoid the warranty. So if you do loose the "bet", just buy annother laptop or pay to get it fixed. On average, if you buy several laptops over the years, this will end up in your favor. However, if you _can't_ afford to fix the laptop or replace it when it dies, then you'd be screwed and its a good idea to get the warranty. For this reason, getting an extended warranty on a wireless mouse is usually silly, but getting an extended warranty on a laptop or other high ticket item makes a lot of sense unless you've got a lot of cash in the bank.
The other question, which I don't know the answer to, is how well they actually support their warranty. Its all well and good to have a piece of paper saying "we'll fix it if it breaks", but if they're in the habit of using the loopholes to get out of replacing things, then you might have just paid $99 for very little protection. Since I've never worked with HP extended warranties, I can't say how good/bad they are.