I think this is an inside joke with the folks who coded DataSet Serialization and Remoting at Microsoft ;-)

Q: Why did the DataSet cross the Remoting Channel in Binary Format?

A: To get serialized as XML!

(crowd laughs)... When you serialize a DataSet, say through remoting, the DataSet gets serialized as XML. So if you're trying to eek out some performance by using Binary Formatting under Remoting, and you pass a DataSet, (here's the punchline), it gets passed as bloated XML.

Luckily, there are a couple of work-arounds presented in these articles ---

http://support.microsoft.com/?id=829740

http://msdn.microsoft.com/msdnmag/issues/02/12/cuttingedge/