Actually, I'm pretty sure the McDonald's thing is because McDonald's has been one of the largest supporters of the Olympics for quite a while now. So it makes sense for them to build a giant fucking McDonald's near where the next Olympics will be held.
As for the issue of cost brought up in the original post, I wouldn't be so quick to judge. You see, there's a reason countries go apeshit when they host the Olympics. They build entirely new record-setting stadiums. They overhaul power grids. They'll practically rebuild an entire city to accommodate the games. And if you think any government will shell out that kind of cash for silly concepts like "honor" or "prestige", well... heh. No, they do it because the Olympics bring in a metric assload of cash to a country.
Now, it may still be silly to host SAM sites in residential areas. But at the same time, you kinda can't blame them for being paranoid. Letting the Olympics get attacked without having done every conceivable thing to prevent it would stain a country's reputation pretty much forever.