I believe in it because it has happened to me recently. BUTTTT, and a big but, it's dangerous to play around with. Because every relationship feels like that in the beginning. It's after about 1 year that you realize whether it's real love at first site or not
When I met my current b/f I turned to my sister that night and told her "I'm going to marry that guy" and he said the same to his aunt (she's always telling me about it). We always talk about how we both fell in love with each other that night. We expressed our love for eachother within 2 weeks of dating