I too read Chris Anderson's book and didn't really find it to be as revolutionary as all of the hype. Free giveaways have been around for as long as people have been conducting trade. Like many digital product authors, I have been concerned about the pressure towards making products cheaper and approaching $0.00. I'm really glad the data and reality have not born this out. Despite the deluge of free icon sets and saturation of the supply side, my business has been just about doubling every year for the past 4 years. I'm also getting more requests than ever for custom icon sets.
Just yesterday I successfully pushed back on a marketplace I won't name and refused to sell my products at the price they set. It is ironic that in the age of FREE, sites like iStockPhoto that operate on an outdated model where authors get only 20-30% commission on their own works and pretty bad terms that overwhelmingly favor the marketplace owner and not the authors are becoming a thing of the past. This, too, is a result of the supply side, though. There is such a large supply of marketplaces that authors don't have to settle for whatever terms are dictated by the one or two marketplaces available.
I know that Iconfinder makes building good, personal relationships with authors a priority and you go out of your way to accommodate each author. You recognize that we are dependent on one another. The spirit is more cooperative and less dictatorial.
My projection is that as more-and-more free options become available and the quality of those options improves, it's not the high-end "premium" designers who will be squeezed out but those in the middle. Other industries have shown that there will always be a market for high-end, high-cost "expert" work and the low-end, super-low-cost bad work. It is an interesting phenomenon that it's the middle, competent-but-not-stellar work that gets devalued the most.
Even in the age of $99 logos, designers can still command $2,000 for a logo because a $99 quick-turn business doesn't offer the personal, face-to-face relationship side of doing business.