In almost no time, the new PSP has been hacked to allow web browsing additions, IM and TiVo playback abilities (among other things).
Hacks such as these often violate copyright law. They might also be a breach of contract some companies specifically prohibit hacking in their End User Licence Agreements.
But regardless of whether Sony can legally stop the hackers, there's a business decision to be made regarding whether Sony should even try.
Sony hasn't had much luck cracking down on hackers in the past. For example, it once sued one of its customers for hacking Aibo, the company's robotic dog toy. This strategy backfired when fans started boycotting the product.
The other downside, of course, is that hacking can raise interest in a product and help promote product sales.