New Media Age has an interesting article (sorry, sub. required) on the business Sony has generated with the launch of the PSP. Brands like Nike and media giants like MTV and Conde Nast have started creating content specifically for the PSP, which isn't simply a gaming device but it's most of all a source of entertainment. A good example is the Tv program Dubplate Drama which last was screened first on the PSP and later aired on Channel 4 and MTV.
What is interesting to note is also that Sony isn't exploring yet the option of offer to brands linear broadcast advertising on the device. According to Andy Reynolds, online product manager at Sony Computer Entertainment, the idea has been discussed internally but, at the moment, there is "no real need to place advertising within each piece of content".
So, according to Sony, branded content is good, direct advertising is not. Also, according to industry experts, Sony is focusing its efforts on yourpsp.com website to make it the "the PSP iTunes", given the range of (free!) content it's offering.