I can see where we're heading with this idea. You're right -- to gain noteriety (karma), a user could easily engage in submission abuse. Submit enough links and enough will get upmodded.

Points, or karma, could be rewarded based off a ratio of useful contribution to total contributions instead. Such a system would encourage a user to make sure his contributions to the community are good. This would be beneficial implemented in any crowd-generated news site.

While not another news aggregator, our project is addressing similar types of issues in other channels. I am loving the applied relevancy to here already.