In regards to the question about proprietary discs..........
"A UMD (Universal Media Disc) is a new, proprietary, high-capacity optical medium enabling game software, full-motion video and other forms of digital entertainment content such as movies and music, to be stored. The newly developed UMD is the next-generation compact storage media and at only 60mm in diameter, can store up to 1.8GB of digital data, making it perfect for a portable entertainment player like the PSP system. UMD stores a broad range of digital entertainment content including games, music, movies, and more. "
see more FAQs here:
http://www.us.playstation.com/psp.aspx?id=faq#4