As mentioned in thisthis question about raw chicken - some people and cultures do indeed eat raw chicken.
Notwithstanding that, to answer your question more directly, the main problem with eating raw meat, fish, or anything else, are bacteria, parasites and other pathogens.
A healthy animal, however, butchered appropriately, should have no specific issues. As such, we make beef tartare, sashimi (sushi refers to the rice, not the raw fish) and just enjoy!
