I said this as a reply, but I thought it warranted repeating.

I would never give negative feedback about a former employee to anyone ever. I have no guarantee that that information is private, and they could sue me for defamation or a whole host of other things if they found out, especially if it ended up causing them not to get a job. That's real damages.

I know I'm not the only one who feels this way. In fact every hiring manager I've ever talked to about this has said the same thing.

I think they only way I'd feel comfortable giving negative feedback is if you insured me against lawsuits due to my feedback, to the tune of many millions of dollars. And even though I'm not so sure I'd do it.