I read this just few minutes ago in digg.com good domains....!! i checked my.com because its the only 2 letter domain from the list.
parking is eaassy when you have thousands of domains. Most people holding large portfolios it's better for them to spend their time buying more domains rather than developing 1 in terms of the bottom line.
Developed domain names always have the potential to be worth more than parked domain names. Take business.com for example, it was purchased for $7 million in 1999 then later developed and resold for $350 million.