I don't think authorities ever helped this idea. The rebuttals I've seen have always been tenuous at best (maybe it's hard to rebut such wild claims) and when you hear things like the original footage was taped over due to a shortage of tape it doesn't seem all that surprising that people will be skeptical. Interestingly, the wiki page (http://en.wikipedia.org/wiki/Apollo_Moon_Landing_hoax_conspi...) probably does the best broad analysis I've read.