The catch would probably "invasion of privacy" since you can basically look into the dealers' books, among other things. It not only tells you the history but also ALOT of info on the owners/dealers along with it.
edit : I only did it this once for Frank as a gesture to the 986 community. Please don't PM me to death with VINs.
Subanez : If you really want to know, PM me.
Anyone else : Again, please don't PM me to death. If its a dire need to know I'll concider having it looked up for you. But you may not like what you find out