The common visual representation of a 'good idea' is something like this:
I'm unaware of any universal image representing the opposite, but might I suggest something like this?
I'd say that after reading an article like that, I'm at a loss for words, but I'm not. It's just that I can't really use the words that I'm not at a loss for. I'm sorely tempted to regress into a fit of bathroom humor and innuendo (like 'just friggin' brilliant', for a tame example). It's still a big yetzer ha-ra for me. But I'll hold off and keep AlanLaz happy.