I have studied the Domain Parking Business with over 130 domain names and published some of the research. Check it out at
www.DomainParkingGuru.com The main reason to park is that it is so easy and fast. It is never wrong to park. The worst crime is to not park at all. That just leads to tp page not found surfing and makes no one happy. Kinda like a left for dead property in a neighborhood.
But I also found a bunch of great alternatives to domain parking in turnkey Private label opportunities. They are almost as easy to set and offer additional features such as Links back out and the CPM are in a whole other league. I have compiled list of free Private label opportunities at
www.PrivateLabelHQ.com