I think we all have had situations like that: once we're involved and committed, they start crawling out of the woodwork.
Case in point: I had JUST made up my mind to date Bruce exclusively.� THEN the guy on campus I'd been hanging out with for ages confesses more than just-friendly feelings towards me.� My thought process was something along the lines of: "And where the FUCK were you 3 months ago when I was SINGLE??!?"� Or the guy I met online.� Or the OTHER guy.� Gimme a freakin' break!
My theory: we ooze "relationship happiness" and people are drawn to us because of it.