Eating raw or very rare beef is always a bit risky. Beef has the potential for carrying salmonella or E. coli contamination. And even when the meat is produced under the most ideal conditions, there is still a risk that it can harbor bacteria. The only way to fully guarantee that it is bacteria-free is to buy meat that has been irradiated. And ground beef is more risky than, say, a steak, because it is handled more, and after being ground it has greater surface area on which to harbor bacteria.