Articles with "WWJD?" are worn by Christians to promote and/or reflect the idea that in times of conflict or moral dilemna, one should speculate (based on the teachings and behaviors described in the Gospels) what Jesus would probably have done in the given situation.
"WWJD? Well for starters, he probably wouldn't purchase and wear tacky jewelry."
"Why is exclaiming 'Jesus Christ!' considered taking the Lord's name in vain, but wearing tacky 'WWJD?' jewelry isn't?"
You: (Think WWJD. Jesus would tell the truth.) Yes, I cheated on the exam today, Mr. Smith.
Frank: Come on now Jon, WWJD?
Jon: You're right... I can't stop now, I've still got half a burger left.