I think the idea that this can be some sort of indicator of intelligence is sad in itself. I am a carpenter, I use geometry every single day, but if you had to ask me to outline any theorems, we would have a problem.
I would simply say that a lot of people simply weren't paying that much attention. It's setup like a riddle because were that actually represented in a correct mathematical way, it would read: (1^15-1)+(1*0)... or something along those lines.
Here is one: Two brothers get paid $100 to till and plant a field, and decide to split that in half. Brother A can till his half in 40 minutes, but takes 70 minutes to plant, and brother be can till his half in 50 minutes but takes only 20 minutes to plant, how much money does brother b get? It's simple really, he gets $50. But most people will see all the numbers and give up, but the answer is in the first line of the riddle.
People just saw the multiply times zero, and saw it at the end, so they simply did it in order then multiplied that number times zero. People are lazy, and a bit stupid, but I don't think this means anything dramatic for the human race... and also, it's facebook... gimme a break.