In comments here, Mike of Angle provides some expert opinion:

1) The vast majority of print publications--newspapers and magazines--are sold for less than it costs to print, ship, and distribute them. If you're going to make a profit, it's going to come from advertisers. This makes their voice more powerful than readers'.

2) It's always easier to justify displeasure on the part of readers than advertisers. If you have 10,000,000 daily readers (5,000,000 that actually pay for it, and a rate-base of 8,500,000) and 2,000 advertisers, it's easier and cheaper to replace 100, 1,000, or even 10,000 readers than x dollars of ad contracts. And their logic is correct. How many of us still deliver our eyeballs to--or even pay for--the NYT, after Judith Miller? Sure it made us mad, but we still read.

3) Advertiser displeasure is felt immediately and goes straight to the bottom line: "Mr. DeBeers is on line four and he's hopping mad about the article on diamond-mining." Reader displeasure is felt mostly in retrospect: "Dear Sirs, I was deeply dismayed to read your irresponsible and one-sided blah-blah-blah..." "Well, we've gotten twenty of these. Maybe we should consider running an Ombudsman feature." "Ahh, don't worry about it--they'll find something else to complain about tomorrow."

4) What each advertiser provides is significant and concrete--x dollars of business--while what each reader provides is variable, miniscule, and difficult to quantify. I would imagine that a publication gets its circ audited no more than twice a year, and smaller publications even less frequently. If you run something that an advertiser doesn't like, you lose money today, and you know exactly how much you lose. If you run something a reader doesn't like, perhaps they write a letter; and perhaps they stop reading. But unless they also convince 100 of their friends to stop reading, the impact is vanishingly small. And even when it's not infinitesimal (rare), and can be tied definitively to x or y article (difficult), there is the assumption with a mass-market product that 100 readers paying 75 cents can be replaced a lot more cheaply and easily than an advertiser that pulls $100,000 worth of ads. Losing readers only costs you money if its significant enough to drop below your rate-base (which is usually lower than your readership, to give advertisers a good deal). A single article cannot lose you 1% of your circ, but it can cost you 1% of your advertising. If you're going to err, you err on the side of pissing off readers, not advertisers.

The proliferation of purely advertiser-supported venues since 1950 has made print much more susceptible to advertiser pressure. The lag time between cause and effect makes advertiser pressure much more immediate, targeted, and painful than reader discomfort. And the short-term nature of capitalism (and any publicly traded business) only increases these effects.

To be blunt--and with all due respect to anybody who disagrees--to believe that readers exert anywhere near the pressure that advertisers do, shows merely that the speaker has never been the editor or publisher of anything. But people WANT to believe this, because they're used to getting the Sunday NYT for cheap.

If you want a publication to be independent, you must be willing to pay the freight. Publications are not magically exempted from the rules of capitalism just because we wish they were.