The vast majority of us aren't taking them seriously for obvious reasons. Their mathematical formula supposedly taken from the Bible is just absolutely ridiculous for one thing. Jesus himself specifically says that nobody will know in advance when he is coming back for another. This also isn't exactly Harold Camping's first kick at the can. He predicted the world would end in 1994, but when it didn't happen, he was forced to recalculate. And then some of us subscribe to some other belief system altogether or don't believe in God at all.
Regardless of what you believe though, it is incredibly interesting to see how those who believe their world is about to end are behaving during the limited time they have left.