It was no more careless on Buffy's part than it was on Spike's to team up, on the old principal, "The enemy of my enemy is my friend." Either one could have betrayed the other at any time, but a certain amount of gut feeling, instinct, and just plain desperation on both their parts made what could well have been a total disaster work, and it also foreshadowed, though probably only I and a few other very astute fans actually noticed it at the time, the fantastic partnership that was to come only a few years later.