In order to prevent answer spammers, can we deduct 5 reputation points from someone who decides to post an answer? If the answer was valuable, then it will get up-voted and the usual +10/-10 per up-vote and down-vote applies. The first up-vote will make up for the 5 point investment for a net gain of +5 points.
You can almost think of it as "putting your reputation on the line" when you decide to answer a question and it may even force you to think about whether or not you really know the answer or are confident in it.
I know this is a somewhat radical suggestion to the SE model, but I'm willing to take the down-vote heat to get some discussion going.