i aim for everyday.
if my body needs a break, its get a break. because things come up with work, social life, etc.. it comes out to about 6X per week. however i aim to do SOMETHING 7X per week minimum. even if its not weights.. it could be bicycling, a hike, sex, anything active. if you have a desk job like I have you need to be exercising daily no questions asked, unless you want your metabolism to slow down and you want to get fat and lazy

.. if you have a blue collar job where you are digging ditches all day then working out everyday isn't gonna be necessary as you are already exercising with your job.
it helps to have splits in place where you are working the same muscle group every 4 days.. that is ample recovery time.
you most certainly can get away with training 3-4X per week, however for me this is more than a hobby. this is a way of life. with 24 hours in a day i cannot see how you cannot dedicate 8 hours of that to sleep and just 1 hour to the gym.
the problem with western culture nowadays is that we rather spend 3 hours watching the game or american Idol than working out. up until really the early 20th century people in the US would work hard all day farming, and if they had a white collar job they would walk to work.. now we have cars and office jobs, so there is a lack of exercise. anyone who wants to really change their lifestyle turn the damn tv off and if you need to go somewhere within a few miles of your house jump on your bicycle instead of driving.