During the discussion that sparked the creation of this poll, I too suggested weighting upvotes by the karma of the upvoter. Thinking about it further, I still like the idea, but it would have to be done properly or it could be easily gamed. Example: a small group with relatively low karma could simply upvote every post and comment made by others within that group (a complete directed graph of upvoting). It would not take a particularly large group to be able to artificially inflate its karma at a greater than linear rate.
The quick (and probably flawed) solution I came up with was to have a tiered base amount that is determined by the karma percentile of the upvoter (eg, 75th percentile might get you an additional 2 points, 25-75 1 extra). Furthermore, there is an additional potential bonus based on the karma delta between voter and votee (ie, upvotes from top HN'ers are more valuable to newbs than to other top HN'ers). As an example, we'll say that we add one point for every 25% tier between the voter and votee (no bonus if they are the same). Using this example, a top-tier vote would be worth 5 points to a newb but 3 to a veteran.
This would allow high-quality posters with more recent accounts to quickly gain the necessary karma for voting, polls, etc without causing such massive karma inflation on the high end.