Sony has just released the second-ever downloadable PSP demo, which runs off the memory stick (first being the LocoRoco demo released roughly a month ago). This is probably another incentive for users to update to the newly released 2.71 firmware, which probably covers up some kind of security hole, besides the minor additions they made in the new firmware. This new memory-stick playable game is called Kazuo, a Soduko-like puzzle game, offered in Japanese language.
Looks like Sony is getting a habit of releasing a new downloadable demo with every minor firmware release, which isn't neccessarily a bad thing, especially for those prefer to keep their PSP 'clean' of homebrew, although often, it tricks avid homebrew users into updating their PSPs as well. Just beware and think twice about updating your PSP, and you should be fine!
Check out more information and download the Kazuo PSP-downloadable demo from Sony
here.