When the SP worth estimates came out (obtained by on-line estimators), I checked another outdoor site for comparison. That other site was shown to have similar worth; the other site accepts advertising, and is also pay-for-use for most information. In fact, I know the net yearly income of that other site -- when one subtracts operating expenses (including business licenses and tax) -- is about 5% of the estimated "worth."
Given that the majority of us are using an ad-blocker, what do you think the click-through income is for SP? If the founders make any profit from this, more power to 'em. They don't charge us, and the people who complain the most about free use of our hard work usually contribute the least.
But there are good reasons for becoming an elf:
1) Speaking engagements gratuities, due to high community esteem;
2) The huge REI elf-membership refunds;
3) Unlimited supplies of Ketracel-white.