My grandpa was circumcised in his 70's - I have no idea why, though I know it was health-related (or at least that's what they were told). I was 7 or 8 years old at the time - it was the late 60's.
I have an Internet friend who was circumcised as an adult because of paraphimosis - definitely not his choice, and he's still unhappy aobut it.
I have a coworker whose husband chose to get circumcised (she told me this when I was pregnant, and the subject came up). I don't know her well enough to ask for details, though I got the impression it was primarily a "locker room" concern for him. I would love to know how they both feel about it now, 15 years later.
A neighbor's son was circumcised at age 5 - I would bet big money that the diagnosis was "phimosis".