Got this from Bing. Seems Microsoft has removed some features from the core framework and added it to a separate optional(?) framework component.
To quote from MSDN (http://msdn.microsoft.com/en-us/library/cc656912.aspx)
The .NET Framework 4 Client Profile
does not include the following
features. You must install the .NET
Framework 4 to use these features in
your application:* ASP.NET * Advanced Windows Communication Foundation (WCF) functionality * .NET Framework Data Provider for Oracle * MSBuild for compiling