2. When someone upvotes or downvotes, all followers of that person upvote or downvote the same submission or comment by proxy. If a person follows multiple people some of whom upvote and some downvote, or upvotes or downvotes himself, then cancel their proxy vote. This proxy voting is the sole purpose of the follow graph, eg. "I want to vote the same way tptacek, cperciva and pg do".
Perhaps publish a leaderboard of top followed people and their voting history to try and avoid a Digg situation.
Perhaps limit the number of people one person can follow. This would help with performance as well.
Perhaps the number of proxy votes would need to affect the score of a comment or submission logarithmically instead of linearly.
Edit: there may need to be a minimum level of karma needed to proxy vote to avoid sockpuppets. Perhaps limit it to active accounts, too.
The problem is that popularity is not indicative of quality.
Your proposal is just another way of staging a popularity contest for comments.
Only instead of having "direct democracy" ("rule of the mob"), you propose a "representative democracy" ("rule of the elites").
While there's something to be said for the "representative democracy" approach (namely, that at least the elites are familiar with the community's norms and mores, unlike some random newbie) they are just as susceptible to making poor decisions as the mob is.
In other words, just because some guy is popular does not mean he makes good decisions.