I prefer that a relatively well worded but completely wrong answer remain but be downvoted so that future readers know that it is a Bad Thing. The more comments on the answer that explain why it's bad, the better.

I only flag answers that are:

1. Obviously shilling for a product.
2. Completely unintelligible.
3. "Me too!"
4. Asking a question of the poster.
5. And sometimes: is so hideously formatted that it would take more than 15 minutes to correct.

Keeping bad answers around for posterity is a Good Thing.

I prefer that a relatively well worded but completely wrong answer remain but be downvoted so that future readers know that it is a Bad Thing. The more comments on the answer that explain why it's bad, the better.

I only flag answers that are:

1. Obviously shilling for a product.
2. Completely unintelligible.
3. "Me too!"
4. Asking a question of the poster.
5. And sometimes: is so hideously formatted that it would take more than 15 minutes to correct.

Keeping bad answers around for posterity is a Good Thing.

EDIT:

Ah, but what about keeping dangerous answers around?

I think that dangerous answers, sufficiently downvoted and commented, should be kept around. That will teach future readers what should be avoided at all costs. Who knows what similarly dangerous answers lie out there on the 'tubes, on forums that don't have the same merit system with easily ranked answers. Mayhaps the same or similar dangerous advice on a lesser forum will not as easily be seen for the dangerous thing it is. On ServerFault, with its easily understood +/- system, an answer downvoted into the cellar will plainly teach that this is a dastardly thing. The comments usually tell why it's so dangerous.

I don't think viewers should be kept from seeing dangerous things, just kept from thinking they're anything other than dangerous.