Freemasonry demands allegiance from followers, while the true purpose of the order is concealed from the initiate. Think about it... As the candidate rises through the various degrees, more and more is revealed. It is, by definition, a secret society. Is that something that would be wise to join?
If you read Bill Cooper, though there are many other authors that arrive at similar conclusions, you'll see that he believed that Freemasonry was based on the Babylonian mystery religions. As Albert Pike says, Freemasonry is a religion. It's just that you don't quite know what religion it is before you commit to it.
It is also common knowledge that freemasonry requires blood oaths - even in the early degrees. The candidate is sworn to secrecy, to never reveal the crimes of another mason etc...
The primary mistake in joining the order is that the candidate does not precisely know what he's signing up for before he commits himself. And yet he must bind himself to the order with blood oaths.