Why the Buffy and Spike relationship?

Long ago, it was Joss' idea that Spike would start to get a crush on Buffy. We had no idea where we would go with that at the time. It was just like, "Doesn't it seem like he'd become obsessed with a woman who could beat him up so badly?" Spike has always been drawn to women who abuse him. So now, with Buffy, this is the ultimate. But once he got the chip, he started to develop scruples, against his will. I think he genuinely cares for her and cares for her goodness. At this point, that means something to him.