FSMO Role - Domain Wide Role

The book says that the 3 roles of Domain Wide Role can only be operated by one single DC in a Forest, but when I was doing my lab I was actually able to seize transfer one of this 3 roles to different DC across my forest.
I transferred Infrastructure, RID, and PDC to different BDC across my forest almost scattered all over the place and was able to and still works.
This contradicts what the book says, I need explanation!
Thanks in advance!!!
I transferred Infrastructure, RID, and PDC to different BDC across my forest almost scattered all over the place and was able to and still works.
This contradicts what the book says, I need explanation!
Thanks in advance!!!
Comments
Edit: Just found this. A good doc on FSMO placement recommendations:
http://support.microsoft.com/kb/223346
You want to set the servers with the best hi-availability and redundancy possible. In small companies, when people first start building their domain they usually put it on 1 crappy desktop or something. In 3 years the company could have grown to 300 employees and you need to move those roles off that server to the nice shiny Dell 2950 you just bought. You wouldn't be able to do this if those roles were not interchangeable.
You may learn something!
Yes, for an AD 2000/3 domain all those rolls are necessary and automatic. Don't let the names confuse you, each one also has additional responsibilities not reflected in the name. For instance, the PDC emulator is also the default Time Server for the domain.