I concur with bstpierre that location doesn't normally give enough information in and of itself; however, I personally think adding the location provides additional helpful information, and is important, whether or not having tags to convey this information is important.
Tags would be helpful to allow users to see groups of questions from a specific area, anyhow—rather than being a method of educating answerers about the facts.
Location can tell you more than just some potentially incorrect climate data (although questioners might take their unusual weather for granted and not mention it, whether or not they mention location, if it's all they're used to). It can give you an idea about what pests might be present, elevation, magnetic fields, diseases, laws, culture, day length, etc.
I don't think something less specific than a state (for the USA, anyway), would be terribly helpful, however, when you could just say the state instead.
In conclusion, I'm slightly in favor of the idea of having non-mandatory location tags (specific—not super general tags that encompass huge areas like the PNW, the Rocky Mountains, or just the country, if it's huge), but I think the specific location should still be mentioned in the question, even if you tag it. People don't always look at the tags, anyway. I think they're nice for badges and browsing, but I don't like it when questioners only put important pieces of information in tags (whether here or any other SE site).