I've already refuted the one about knowing who is the father of the child. In your link, there is a bunch of Muslim beliefs. I am not Muslim, and I reject Muslim teachings. The only reason I saw listed was in order to provide husbands for women. This assumes there are not enough men to marry the women. This is false, since up until about the age of 70, there are more men than women. The only reason there are more women on earth than men at any given time is that women live longer. If that logic is to be applied, then women should be the ones to be able to have multiple husbands, not men. For the record, I believe both to be immoral.
I have in my personal experiences seen very little bad things from it.