It's that kind of situation that Laurie, a colleague and friend of mine, painted for me as we were on our way home from work tonight. She'd met him a couple of months ago while on a vacation with her girlfriends and what ensued was a love affair out of a chick lit book, no kidding. Even though he lived in a totally different time zone, they'd made a connection and soon he was flying in to see her, they were spending time meeting each other's friends and family and he even came to a work party to meet her colleagues! We all suspected it was going somewhere and were way too happy that she found a storybook relationship with a great guy without even trying.
Anyway, during one of their visits together, they'd had the "DTR" (or, "defining the relationship") talk, in which he mentioned that because of their extreme distance (an ocean, at least) that exclusivity may not have been the best option for them. Now at this point, she's clear that she likes where they're going and doesn't want to see anyone else, which she tells him. In spite of the heavy topic, they managed to have a great weekend, which put her concerns aside.
However, when things got weird during their extended vacation, she knew it was different - and just like that, he thought it was best they stay friends. They still communicate often and have maintained a friendship, but it leveled off from their budding romance.
As Laurie told me this, I was admittedly confused for her. It was clear his wall went up fast, probably when she told him how she felt. But for a guy that started the chase in the first place, it just makes no sense that he backed out, especially after all the effort.
In breaking it down in my own head, I found myself wondering if he was caught up in the magic or thrill of it all as opposed to wanting to commit to anything long-term. I mean, did the deeper feelings she had make the situation more "work" and less fun? Honestly, I'm not sure. But my theory is that you don't mind putting in the effort when you want your other half to stay in it for the long haul.
Ultimately, you can never predict what happens after you start seeing someone. Will they stick around? Will they fade? Will they still be in the picture in a year, a month, a week? Sometimes, you may just have to take your chances and hope that the vibe you share should be enough so that nothing -- not even the "defining the relationship" talk -- will weaken it.