The Times tried this once before and discovered nobody paid. What did occur was that the Times became dramatically less relevant to current discussions, many of which take place online.
Links to the often interesting columns of David Brooks will be missing from this and other blogs. Missing, that is, unless Brooks is syndicated to newspapers which do not follow the Times behind a paywall.
Some op-ed content of The Wall Street Journal has been behind a paywall for months now. I often find there are ways to link to this content if I am creative; perhaps the same will be true of Times content.