I can't speak to the US experience but it's basically the same deal in Australia - a good friend of mine got her spouse visa literally overnight from the Tokyo embassy, but I've heard stories about it taking 18 months to receive the same thing if the applicant is from a developing country.
The situation truly sucks, and I wish they could do a better, faster and more dignity-preserving job, but there is a lot of fraud and motivations of the applicant can often be questionable. A thai-chinese friend once told me that one of her friends needed to marry an Australian for visa reasons, and would pay $25k or more. That opened my eyes a bit. She could just make that much more working here. Guess the occupation.
There's no excuse, but they do have a lot to deal with.