As a moderator over at physics.se as well as a Stack Overflow user, I've noticed the unfortunate habit of some users to "serial down-vote" answers that are not apparently incorrect. This a rare occurrence, but nonetheless one that is noticeable. The idea here is encourage constructive criticism and feedback rather than "I disagree with this, that, and that, but I don't fancy telling anyone why." (From my personal experience, such supposed users, when having been politely asked to leave reasons, very rarely do.) I can only suspect this is done by a small minority of users, but is certainly noticeable enough.
As a moderator, I am able to see the number of votes cast by users on other users in certain cases, but not of course specific up/down-votes. In the desire to stop this detrimental habit, what do people think about providing a (moderator-only?) capability to view users who are serially up-voting or down-voting? I'm mainly just interested in gauging reaction of other users (particularly moderators). This is likely to be a highly unpopular idea to most, though it does not necessarily mean that it's a bad one.
In addition, I'm also curious what other ideas people have to encourage feedback of the more constructive variety. (Most users are already sensible enough to do this, but again, there's a significant minority out there who don't.)