Did you know that when doing contract first development and utilize a Boolean data type with a default value (lets just say the default value was set to true), WCF will not serialize out the default value in the message. WCF will only serialize out the value if it differs from the default.
This was an interesting scenario in BizTalk when we were trying to test for the Boolean to be true and we saw that it was actually empty.
Sometimes I wonder with these types of issues if I am the only one in the world that didn't know that. I am going to make the assumption that this will be news to more people then just me.