I vividly remember oldsters eating raw hamburger when I was a kid. Can't imagine doing it now.
"Steak tartare". My grandfather was a butcher, per Mom, he ground the beef himself, chopped onion up right in it, added S&P, and slapped it on Italian bread.
Steak tartare is definitely different from ground hamburger because steak tartare is, well, freshly ground steak, while hamburger is ground god knows what ground god knows when. Steak tartare with Tabasco, Worchestershire, raw egg, capers, raw onion, and toast points. That's a fairly modern dish that can now only be found in historical cookbooks. Joe Allen's, in NYC's theater district, was famous for its Steak Tartare. Key word: was.
I hear so many warnings on cooking shows about hamburger. They say to let beef come to room temperature for up to a half an hour before cooking -- except hamburger. And they're adamant about that. I never heard such a warning when I was a kid.
Which is why I put it in quotation marks.
For those who are immensely concerned about meat pathogens in hamburger, even grinding steak yourself, then, is no panacea because there's always a chance the surface of the meat has been contaminated; grinding it up just mixes it up throughout the meat in that case.
As for myself, I'm not too worried about it. We'll cook and eat med-rare burgers at home and have done so for some time with no ill effect. NC passed a law years ago making it illegal for restaurants to serve burgers cooked any way other than well-done, so, bleh.
I'm very careful about handling chicken, though, and eggs.