[retroafroman]

I wouldn't. At one job, the desks were arranged so that I sat at my computer with my back to my coworker (who talked to himself/no-one-in-particular/me throughout the day) and I could never tell when he was trying to talk to me or just vocalizing something. Also, I found it annoying. A small annoyance, sure, but if it bothers your other developer's, it's not a good idea.

[icefox]

Well if you were doing the hiring I am guessing you can also set the seating.

[retroafroman]

Good point, as long as it is possible to place the self-talker in a place where others aren't bothered, whether that's alone, or with people who aren't bothered, it wouldn't be too bad.