Yeah, for me - across the board of the entire story - the most alarming thing is that there seems to be little blowback against McDonalds for this. Considering how much that promotion was "worth" to them and how much business they got because of it, they lost almost nothing for misrepresenting the chances of winning to their customers (which they could have prevented if they were a little more careful). If I were a McDonalds exec, the unfortunate moral I would draw from this is to rig the game for myself next time, because it doesn't hurt the company at all, really.

They tried. From the closing paragraphs of the article:

"A group of Burger King restaurants tried to get a class act lawsuit together, so did a group of unhappy McDonald’s customers in Canada."

Wouldn't even surprise me if this was defacto behaviour for most large contests managed in the USA.