What type of meat do you use for hamburgers?

 If
you are grinding at home there is little need to worry about cooking temp
because your meat shouldn’t be contaminated, so you can make a medium moist
burger.

Is this true?   When you cook a steak, the heat kills the bacteria on the outer surface, but the inner section of the steak has never been exposed to the "elements", so contamination is not so much an issue.  But even if you grind your own meat, aren't you now mixing the outer contaminated surface into/throughout the burger meat?

On another note, anyone ever eaten at Ray's Hell Burger?   That was the first (and only) time I've ever eaten a burger and didn't need to add condiments... yum....