This thread is interesting... I thought I'd give my two cents since I'm err, well past the point of beginning.
Disclaimer: Married my Aikido teacher (been together for 3 years this month) and we're welcoming our first child later this year. We have a large age difference (12 years) but we don't really notice it.
God writing it down like that sounds so bad but it might just be how society perceives it. When I think about HOW we began to like each other and pursued each other, it doesn't seem so weird after all. I didn't like him because he was my teacher, and I liked him after we got to know each other off the mat. We just clicked as people, Aikido happened to be a mutual hobby.
To be honest I didn't think he was so remarkable as a person on the mat, sure he had great technique and was a great teacher but... I went to learn, not to develop a romantic relationship. And you know, he was bland and dry and just... I don't know, kind of an old fart even though he's quite young. Not the kind of guy I would have went for if he was that way on and off the mat.
We run the dojo like a family still, even now. I cook for the seminars, direct cleaning, deal with marketing, finances, etc. I do miss practicing but the pregnancy has been hard and somewhat risky but I still try to be as involved as possible.
I know from his point of view he tried really hard to distance himself from me. He stopped teaching some of the classes that I attended, and he kept telling himself that it would be okay if we were just friends, and he'd be totally fine with that. I probably wouldn't have liked him though if we didn't attend some parties of mutual friends together and got to talking at those times because we didn't really know anyone else other than the host. We were friendly with each other and it just developed into something more by itself. Maybe we were flirting without realizing it, because thinking back we didn't tease or play around on or off the mat, we just talked about life and a some personal things and that's where our relationship stemmed from,
I don't know. True love, compatibility, I can say that I found these things with him and it can get rocky at times so setting boundaries in the conduct in the dojo despite a relationship is important so that whatever you guys are going through does not affect how the dojo is run. It's not impossible for there to be a happy ending (although what do I know, still got an entire life ahead of me) but I think it's not about one person liking the other or pursuing the other, it's about two people walking closer to the same path.
I personally don't think a relationship can be built upon a student teacher relationship or BECAUSE of the teaching of the instructor or BECAUSE of the hobby--an imbalance in power and I don't think that's what love is about. It can be built when two people, off the mat, click more than on the mat, that they as people match each other, not just being in awe of each other's ability. What I mean is, if I never practiced Aikido again, if he never taught me another technique, if I stopped being involved in the dojo (which I have occasionally due to health or other reasons) we'd still be together and in love. So I think that's something you have to ask yourself honestly if you are considering a relationship with a teacher or a student: Can we still be together if Aikido was not involved at all? Can we still survive without that difference of power (i.e. are we equals in real life or does the power imbalance carry on off the mat--if it does, I believe there will be problems)?
Over the years you hear the anecdotes of female students falling in love with their teachers because they are attracted to their skill, I think it may be an evolutionary thing given that in the animal kingdom, the males usually have to put on some sort of display that show their prowess. It often ends badly,like dating a coworker, sometimes it ends up good though, so I think every situation is unique in itself.
Regardless of the tangible situation around, every relationship needs the three C's. Communication, Compromise, and Cuddling. If something's wrong, chances are one or more of those departments are lacking.