Thank god for one sane opinion! And this is what I read today:
"Rational arguments don't usually work on religious people. Otherwise, there wouldn't be religious people."
Apart from selection bias, another thing that influences people big time is confusing correlation with causation.
http://en.wikipedia.org/wiki/Correlation_causation
Koi kahega- "Aaj kaali billi rasta kaat gayi, isliye mera accident ho gaya". While it may be a fact that both things happened quite close to each other, what proves that kaali billi was the reason? Bad stuff happens on a regular basis. And the supposedly bad omens (billi, chheenk, aankh phadakana, etc. etc.) also happen on a regular basis. There is heavy correlation between such common occurrences. It is very easy to attribute something shitty that happened to you to some bad omen/ bhavishyavaani or something funky.
What makes this worse is bhed-chaal. One person would say this.
And then, all his near and dear ones and then near and dear ones of his near and dear ones, would become quick believers of the theory. So the first guy makes the common error of confusing correlation with causation. And once he has peddled his story, every one else goes around actively trying to prove this notion. Many times, nothing happens despite the bad omen/bhavishyavaani. But the reaction then is "Bach gaye!!" rather than "Yeh sab bakwaas hai". This is where selection bias comes into play, as we are biased to give the negative incidents more weightage in selection, while not taking into account the times when nothing happened.