I’d say it’s a bit of a lottery! A lot of the bacteria, spores (sleeping bacteria waiting to find a good host to grow on) and funghi (mould) in the water would probably get killed by your stomach acid, other bacteria and viruses would get killed by your immune system. But depending on what exactly is in that puddle, it might get past your defenses and get you sick. Also, if it’s a puddle in the city, chances are there is some car oil etc. in the water. Not great for digestion. :] It’s not the worst thing you can do, but I’m not sure it would be worth it. 🙂
It might have dog poo in it. I wouldn’t want to take the risk of drinking that, so I’d steer clear.
Then again, if you had something like this, you could go for it: http://www.buylifestraw.com/en/. It’s a water filter, which gets rid of all the bacteria and other stuff, inside a straw. So you could just put your straw in filthy water and drink up (though probably best to check it isn’t too dirty)!