Just happened to read an article on crushes from The Guardian via Pocket on this topic. Psychologist Dorothy Tennov compares crushes to "the intensity an addict feels in the all-consuming pull for drugs: limerent people find themselves doing bizarre things in order to pursue their crush."
My experience with the three true crushes in my life has been that when they are over, I always thought "what the hell was that all about?" The three women I was thinking about were all completely unsuited for me.