Calling in position with deep stacks is definitely something that shouldn't be thrown out the window.
With 130+BB stacks, I call a fairly large chunk of hands in position when a light 3-bettor takes me on from the blinds. His problem, when bluffing (what consists of a "bluff" is vague in this sense, but I'll go with "any hand that he doesn't think has a reasonable chance of being best if we call"), is that he's going to be out of position in a big pot but still fairly much money behind with a mediocre hand on almost every flop.
A 3-bet usually makes the bet between 10 and 16 big blinds. So the pot will be in the 20-30BB range when we hit the flop. On the surface, it would seem that he needs us to fold more than half the time on the flop when we call him in order for him to be "immediately profitable."
Here's the problem with that reasoning: It's not "immediate." There's a flaw in calling it "immediate" profit when an opponent folds often enough to make it an "immediate" profit. You see it a lot pertaining to blind stealing. If the blinds fold often enough, you make an "immediate" profit by stealing.
That's only true if you figure to average a better net than zero postflop when your opponent doesn't fold. And a lot of people are really bad postflop. So if you have negative implied odds
when you see a flop - like, say, being out of position with a mediocre hand in a big pot vs. a decent player - 3-betting light isn't going to be profitable even if your opponent folds just more than the fictitious break-even point.
Of course, it would
be immediately profitable if
our strategy when called was simply to always check/fold. But for how long do you suppose that strategy would be immediately profitable? Heh.
(I hope everyone realizes that I'm not arguing against C9, here, btw. Just a tendency I've noticed for some people to be extremely spewy with 3-bets from the blinds.)
Now, as for countering light 3-bets with 4-bets, this is a valid strategy and should be employed. But not very often. My own bluffing-to-big-hand ratio is just over 1:3 when I 4-bet. I'm tighter than most regulars in that regard, but I have a reason for it: 4-betting being profitable doesn't automatically qualify it as the right play. If there's more money on average to be had from calling, then you should call. Versus the regulars, flatting in position is definitely viable, even - occasionally - as a delayed bluff.
Also, 4-betting means the hand is essentially over preflop; most of the time, our opponent shoves or folds, ending the hand. As you pointed out, the preflop edge for good players vs regulars nowadays isn't that great (by the way, table select!), but if we think we have a postflop edge, we should try to play more flops, not end hands preflop. Especially in position.
I don't know if this comes off as incoherent rambling or not, but I've had a long day, and it was also a topic I have a bunch of pent up stuff to say about. So there.