Don't use store-bought pre-ground beef for this one, kids. You are begging for contamination. Buy a piece of beef and grind it yourself in the food processor.
Another good way to eat raw beef is to take a frozen steak, slice it very, very thinly, and serve it sort of semi-thawed with some kind of dipping sauce. I have had this in Japan and it is fantastic.
It's probably safe most of the time. However, I have a good friend who got a nasty case of parasites from eating raw beef, so if you go that route, you might want to de-worm yourself every once in a while, as people do for their pets.
Personally, I think the invention of cooking is one of man's greatest achievements, and I greatly enjoy the benefits it brings, such as no bugs and easier and more complete digestion.