Don't allow users to answer and vote on the same question
The current -1 penalty discourages legitimate down-voting even when it is deserved. I understand that it is intended to address a conflict of interest (users down-voting competing answers to their own). I don't think that it really works as intended. It doesn't guarantee that people still won't try to game the system in this way but it does discourage down-voting of early-but-wrong answers that were erroneously voted up.
A better option would be to follow Slashdot's lead and not allow a user to vote on questions that they have also answered. If the answer a question after voting, their votes will be cancelled.
not really seeing the problem here
Everyone always thinks there answer is better, this is the root problem with stack over flow, get over 100 rep, and downvote the competition to make you seem more superior. Only reason I don't answer questions.
The current method doesn't particularly discourage early down-voting of incorrect answers, because I can always go back and undo my downvote after more people have upvoted correct answers. I'd argue this is what it's *most* useful at -- temporary reduction of a poor answer so the good answers get better visibility.
Terrible idea -- what if the current answer is wrong, and I have a better one? I would have to either mark the other one down and leave 3-4 comments explaining the actual solution, or write an answer and hope enough people wander by to downvote the other one.