Honestly, I think a lot of it depends on what you are doing for exercise.
If you are a light exerciser, then I think it is fine to take a 1 or 2 mile walk first thing in the morning before you eat anything...but if you are doing a long powerwalk, and it is going to be a longer distance than that (like 3 miles + or something), and you are going at a pretty quick clip to where your heart rate is up and you sweat-you should probably have some fuel before you work out.
Also, if you are doing a light strength training routine like Pilates, or a routine using 2 or 3 pound hand weights you are probably fine not eating immediately before or immediately after a workout-but if you are a serious strength trainer who lifts heavier weights, and lifts to failure (where you fail each muscle group to the point of not being able to do another rep with proper form) then you should fuel a little before you workout, and a little afterwards. (It doesn't always have to be a big thing, but a lot of lifters will have half an energy bar, or a scoop of protein powder to support muscle growth, or something as fuel).
Also, whether you are doing strength or cardio exercise plays a part as well. I will have a bit of fuel right after a strength workout, but not immediately after cardio.
As far as WHEN you exercise...that is up the the individual. I exercise whenever I fit it in for the day. Sometimes this is in the am, other times it is in the afternoon or evening. The only thing I avoid is doing cardio (powerwalking/jogging/aerobics/biking) late in the evening, because I get a "cardio high" that lasts for a couple hours...and I would be unable to fall asleep if I did cardio say at 8pm.