The burden of proof

If you ever go to www.theologyweb.com or the dozens of other places there are where theists and atheists debate each other on message boards, you might notice them shifting the burden of proof back and forth. This makes absolutely no sense to me. Why are they debating there in the first place? Is it simply to win a contest? If so, their shifting of the burden of proof might make sense. Outside of formal debate, though, there’s no point in shifting the burden of proof. The burden of proof is on whoever wants to persuade. You can’t persuade somebody by shifting the burden of proof on them. If you want to convince another person you’re right, the burden is on your shoulders to show them that you’re right. If a person has no desire to pursuade anybody, then they have no obligation to assume the burden of proof.