I was playing around with my stackapps app and noticed a trend that a .Net tag is largely useless and mostly follows [c#]. Have a look at Jon Skeet or Marc Gravell. There is a clear correlation between the two but instead of what seems logical - that c# questions are a subset of .Net questions, it's the other way around. It's almost as if some users tag their questions with [.net] and some don't.
I guess what I am trying to say is whether or not there could be some smarts included in the tag system in the way of "tag A implies tag B". Or even something more elaborate like "C# implies .net OR Mono, you must pick one of those".
Does that make sense? Would it be usable?