A quick back of the napkin math shows that they won't even recover a fraction of the revenue they're foregoing.

This move has nothing to do with ad revenue and everything to do with fighting Murdoch and WSJ. WSJ will go free (mark my words) and will take a away a ton of NYT's traffic. NYT is fortifying its traffic and is trying to boost it before Murdoch makes a direct assault.

Or not. This could be a disaster for them given that people like Friedman actually have a relatively loyal following. Going free is not the answer to everything.

True, but I think the exposure that Friedman will now receive by making his columns free more than offsets the loss of "pay" revenue. This move will enhance both the Times readership and its reputation.