[dLuna]

Since people have to be logged in to vote, there is a much easier solution:

Count votes from new users lower.

And count early votes from users often voting on articles posted by a particular person lower.

It can be refined quite a bit...

[fbnt]

True, but the problem with voting rings is that links may be submitted by different participants to the ring each time, and if they all have genuine high karma, that is difficult to track down.