I've had it come up and thought it was great. In my case, the timing of other offers meant that the potential employer would have to hire me without all of their normal process. That worried them.
I explained that if it didn't work out, there was no sense for either of us in me staying on when it wasn't a good match. We then had a reasonable, adult conversation about hiring and firing and our approaches thereto.
It was honestly part of what sold me on the place. I think that companies that treat firing as some sort of spooky bogeyman are not so good at management. It's not like failing to talk about it means that firing isn't a possible outcome; it just means that people dance around it.
It's an adult approach to work. Like linkedin / Reid Hoffman's approach to career development: stop pretending you're joining a company for life; instead, treat employment as a tour of duty with limited duration. The company gets X from you, and you get Y from the company. At the end, you may or may not choose to re-up, with new goals for both sides.
I explained that if it didn't work out, there was no sense for either of us in me staying on when it wasn't a good match. We then had a reasonable, adult conversation about hiring and firing and our approaches thereto.
It was honestly part of what sold me on the place. I think that companies that treat firing as some sort of spooky bogeyman are not so good at management. It's not like failing to talk about it means that firing isn't a possible outcome; it just means that people dance around it.