I guess that you have all heard the news. Joe Quesada, head of Marvel, had decided to break up Peter and MJ's marriage in a four-part story in which Peter chose to erase several years of his past life in order to maintain his secret identity. Among the casualties were his marriage to MJ and her knowledge that he was Spider-Man.
Apparently, Mr. Quesada believed that Peter aka Spider-Man was more interesting as a single guy and does not believe that superheroes should be married. He even managed to disregard the fact that many Spidey fans did not mind the Parker-Watson marriage one bit.
Personally, I believe that Quesada is a mentally backward idiot.