I think love at first site has a lot to do with physical attraction and pheromones, which are powerful little fuckers. The pheromone thing will always work for ya if you like the way a certain person smells I think, so you will always feel the same thing when their scent is near.
When I fiurst read the title to this thread, I thought you were going to ask me if I believed in gnomes or pixies or something like that. The answer, by the way, is you bet.