Funny you should post this...
There was an article on The Register from 'security expert' Bruce Schneier and 'usability expert' Jakob Nielsen that passwords shouldn't actually be marked at all. No, really...
http://www.theregister.co.uk/2009/06...rds_usability/
What utter rubbish from so-called experts. The comments (for once) on El Reg are actually pretty good.