Naw, we're not getting stupider. My theory is that now that we have an Internet, we can seek out and are exposed to far more idiocy than we would normally experience in our daily lives, surrounded by normal people. Yes, reality tv is reaching new depths, but remember, we put a robot on the surface of another world, and through it we have gained a deeper understanding of potential life on another planet!
Also, to anyone who is treating Idiocracy like a prophetic vision:
http://imgs.xkcd.com/comics/idiocracy.png