If I get more than a couple of dates in, I want to know if you've been engaged and why it didn't work out, because that answer is going to weigh into whether I keep seeing you or not. It's not as heavy a subject as divorce to me, but it'll still give me pause. But to answer the actual question, I think that it depends on the person. Some people would care, and some wouldn't, as evidence by the replies in this thread. You could always play it safe and casually mention it yourself at some point.