From Out of the Woodwork They Come

Can anyone please explain to me why old boyfriends come out of the woodwork when you're seeing someone else? Is there some sort of signal that gets transmitted into the universe and puts them on high alert? I really don't understand the phenomenom, but it always happens the same way. When you're alone, you're really, really alone. However, when you're seeing someone, all of a sudden every boyfriend you've ever had decides that, um, oops, maybe he made a mistake (well, DUH). What's that about? I've never understood why when it rains, it pours. Luckily, I'm not in the market for old boyfriends (today, at least), but if I were, I'd be in luck! :)