I kinda like the HN system of only allowing downvotes if you maintain a comment karma above a certain level. That, or something like that, makes a lot of sense and it can't really be "gamed" by the comment trolls on techcrunch.

Again, my belief is simply that this is not a new problem. The word "troll" has existed since the BBS days and over the last 10 years other sites have come up with clever ways (that work) to filter the trollish comments out. I don't think any of them are perfect, but it seems a bit cynical and overstated to say "any" voting system would be gamed if other sites have managed. Even digg.