Fr. Charles recently posted a tweet in which he said he was uncomfortable with all the ridicule heaped upon the Rapture folks given the prospect of no similar ridicule coming in 2012 when the Mayan calendar supposedly has the world ending.
It's worth considering, but I think there are two defining differences.
One is that the Mayan claim has the patina of age, and thus a tiny slice more credibility. It's one thing to predict in 2009 that the world will end in 2011. It's another to predict it a thousand years earlier (disclaimer: I know nothing about the Mayan calendar thing; merely reporting my impressions which I suspect are not that different from the man on the street). If you predict something will happen well beyond your lifetime you are removing the "credit" you'll receive by the prediction. Tis true you also remove yourself from potential blame if it doesn't happen, but there's something a bit more palatable, in this age of self-promotion and hype, to come up with a calculation way beyond your lifespan. It seems less...arrogant.
Second, the promotion. If the Mayan story came complete with huge billboards and full-page ads in newspapers and someone presumably making money off it, then there's bound to be more ridicule than something that hangs more quietly in the background.