I think not common, at least not in the US. The risk of liability is too great. My company has a strict no-comment policy, and won't affirm anything beyond dates of employment and job title. This seems to be the norm for corporations.
Smaller business who don't have their own HR and legal departments protecting them may be a bit more forthcoming, but probably not much.
Big companies find other ways to do it though. Don't believe for a second that nut job managers won't do everything they can to screw your career if they feel slighted.
