Friend Roy did post:

Microsoft have just pulled their joker out of the hat before the Playstation3 launch. After learning from the original xbox hackers and
giving the 360 a mediacentre, (they did Actually credit the xbox hackers in their launch video), they've now announced that they will not only allow homebrew content on the 360, they are encouraging it!

http://www.gamasutra.com/php-bin/news_index.php?story=10458

And Sony must be sick to their stomach as they were the most well known company for doing this with their PS1 Net Yaroze project.
http://en.wikipedia.org/wiki/Net_Yaroze