I've wanted that feedback as well, and I know others that do. I know I'd generally react favorably to the feedback, using it to improve. However, I think we (people who want this and talk about wanting it and wouldn't go off the deep end) are in a minority. We're writing and talking about it - we (here on HN and blogs and such) tend to have more self-awareness than others - or at least express that self-awareness more than others. But we're in the minority - people would sue, they'd stalk, they'd pester, they'd argue, etc.

Companies love NDAs - how about an NFOA - a Non Freak Out Agreement? Sign it before an interview. If you've signed it, we'll give you honest, open, critical feedback about how you do or don't fit in with the company's needs. Honestly, I do think sometimes I've not gotten a job it was more a personality/culture fit than anything else, but I'd like to know that as well (and frankly wouldn't mind giving them some feedback on their culture too!). But without knowing, perhaps I get too hung up on a linkedlist question and fret about that in future. And turning it around, perhaps the company could get some good feedback on their own operating culture ("no, being on call 24/7 to babysit broken code isn't worth $30k, but you didn't say that in the job description").