Lats act as a stabilizer when you bench. You essentially use your lats to lower the bar. The larger the upper back becomes, the less distance the bar has to move.
Like MC said (maybe we should call him mc hammer..LOL) the compound movements are the key. When you do isolation movements, stick to dumbell shrug and cleans to help the rears and rotators...this is essentially the same as a barbell clean.
Another thing to think about when doing isolation stuff (which again is not as effective as compound movements) is when doing bent laterals...try not to pinch your shoulder blades together at the top of the movement...this will keep the rears working. Again, it is not as effective as compound movements that MC Hammer suggested, but it is worth noting.
I was just mentioning the exercises I'm doing which might have a bearing on the overall area and which might have contributed towards giving me better results than the isolation work I used to do.
I mentioned deads and power shrugs since the traps sit right next to the rear delts and I don't see how the rear delts can come away fresh from a session of either of those exercises. Don't forget that being a support or stabiliser muscle in a heavy compound exercise can often lead to more development than hitting the muscle directly with light isolation work. Thus also the military press.
I've found my lateral delts improving a lot since doing MP. Can't really say they do much for my anterior delts but the movement, along with push press, is a good all-round shoulder exercise. I think the power cleans have been a good contributor to my upper back area of late.
Something has to stabalize the bar while it's being pressed. The back comes into play significantly.
You might really look at snatch grip high pulls. Far far better than upright rows or any of that crap and believe me - the first few you do, you will instantly realize there is significant heavy involvement.
I agree with the philosophy so far in this thread that rows, chins, cleans, etc will bring a lot of rear delt growth, but if want, I don't see anything wrong with adding bent over laterals at 3x10-12 at the end of the day.
I've been thinking lately about the heavy compound exercises in general as against the traditional BBer-type isolation exercises and also machine exercises. The biggest difference in feel seems to be that when you're doing the traditional or machine exercises you generally feel very steady and secure, even safe.
With the big exercises there's no comfort zone. You can feel that there's a lot of body involvement to attain and maintain stability. There's a possibility of everything going tits up and a genuine feeling of risk involved. Even with the difference between something like shrugs and power shrugs you're destabilizing the body and having to keep control of a weight you've just turned into a projectile.
I agree, view, nothing wrong with some high-rep isolation work to get the blood flowing, especially if you enjoy it.
I have heard that an imbalance in strength between rear delts or lats and pushing power makes you more prone to injuries aswell. It is what leads to most shoulder especially cuff injuries. There was an article in FLEX about it this month.