Consider using CAPTCHA to make abuse more costly

[gilch]

Regarding the continuing complaints about mass downvoting and sockpuppetry, consider using CAPTCHA to make abuse a more costly action for the abuser.

A simple start would be to require passing a CAPTCHA for each vote cast. This would make both mass downvoting of individuals and sockpuppet rings voting up each other slower and more difficult, and make scripted attacks impossible.

This has the unfortunate side effect of annoying legitimate users, and reducing their incentive to provide valuable feedback by voting, but this cost might be worth it. The greater certainty per vote may compensate for the lower total votes. We do not allow unregistered users to vote, after all.

Once that is in place, we may be able to add heuristic rules to ease the burden on legitimate users in ways not easy to game, but that can come later.