This logic should also be applied to when past employees call for references. Never give a statement, refer the person calling to your corporate HR department. Your company most likely has a policy for this, in addition if you say something you are not supposed to legally you could open yourself up to a heap of trouble. INAL but I've sat through enough corporate HR presentations to have this hammered home and hopefully can share this with startups who haven't had the benefit of an experienced HR team.