The only people I know who don't do a residency are people who want to go into industry (e.g. work for a pharmaceutical company), are MD/JD, or do something like public health (although there are public health residencies and most true MD/MPH practicioners have done a residency). Bottom line, practically nobody sees patients without having done a residency first. Among other things, I imagine it would be damn hard to get malpractice insurance. As a 4th year med student (MD minus 3 months), I can tell you I would not be comfortable sending my grandmother or any relative of mine to one of my classmates until after they complete a residency -- med school prepares you very well for residency, but not to be out alone practicing somewhere. Even after you graduate, you still have a lot to learn.
bpkurtz