Well, interesting one this...
I'm going to sit myself somewhere in the middle and say you should use whichever lights you can justify with considerate thinking.
In all my time driving, I've probably used my rear foglight(s) fewer times than I could count on the fingers of one hand - well, in fog anyway, the count would increase if we included instances of flashing it/them to indicate to someone I've just passed that theirs is/are on for no good reason.
On the cars I've had with front fogs, I've used them now and then, but I think it'd be fair to say there's generally a reasonable motive...
1) If there is pretty thick fog (I'm talking visibility down to 50 yards or less) - they do help. Sometimes I'll use the fronts and not bother with the rear - On most, if not all of the cars I've owned, the tail-lights have been perfectly bright enough for anyone to see me a good distance away even in bad fog; so the rear fog light just becomes an item of no use other than dazzling and distracting the drivers behind me.
2) If I'm driving down an extremely narrow, windy, deserted road in the middle of nowhere in the pitch dark - sometimes you need as many lumens up front as you can get - it's perfectly justifiable to have main beam on in these circumstances, and being confident I can kill the fogs as quickly as I can kill the main beams leads me to think I'm not being too much of an **** employing the additional light.
3) I have, on occassion, done sidelights and front fogs. Again though, I try to consider when and why... I ALWAYS drive with my sidelights on - first of all, I'm never going to dazzle anyone with those, and they can only improve my visibility to other road users. Again, in certain road conditions (perhaps out in the sticks again, on a quick road with failing light) I feel that it's prudent to have as much lighting indicating my presence as possible, but stopping short of using dipped-beam - The company car is a MY09 Modeo Estate and it has beeeeeeerilliant headlights - I'm the last person on earth to go Audi-bashing, but the headlights on it absolutely rip the **** out of the units we're used to. One side effect of that is that it only takes a little bump in the road and you can dazzle people needlessly if you're using them before it's properly dark - and this isn't just limited to the Mondeo bus, I've been 'dazzled in daylight' by folks using the dipped beam before it was strictly necessary plenty of times.
...Considering situations like that, I don't think it's
always a sin to use sides and front fogs.
...I will quickly add that as soon as I'm on a slower, wider, well-lit road (in a built-up area for example), I'll revert to sides only.
...Oh, and the only other time I use the front fogs is when I flash them alternately with the main beam - this is useful for scaring the s**t out of colleagues you are following without their knowledge - the same can be said for chumps who cut you up etc. The split second of them thinking they've carved-up plod and are going to be surprise buttsecksed for it is priceless
Regards,
Rob.