[js2]

Pretty sure it's a US/UK thing.

[seabass-labrax]

Historically speaking, it's common to both UK and US English because it predates the European colonization of America:

http://www.miketodd.net/encyc/gotten.htm

Personally, for a situation like this I'd use the somewhat more formal 'become' instead!

[lysace]

Agreed. "got" is more informal and less universal across variants of the English language than "become". Bad editing.

[graemep]

Given "got" is used in both British and American English and "gotten" is used only in American English (I do not think it is used in other variants either) I do not agree about "universal"

[lysace]

I meant to agree that "become" should have been used instead.