Rather quickly, the original CAPTCHAs have become a nuisance. reCAPTCHA on the other hand has, as von Ahn et al. write, “a positive impact on modern society by helping digitize human knowledge.” Univocally, it is true; reCAPTCHA assists in the digitization of human “knowledge.” But the two necessary supporting ideological proofs – digitization of human knowledge is entirely good and the coercion humans to do that work is beneficial for the whole of society – are far from universal truths. Who reaps those rewards? 
In one interview with von Ahn, he and Clive Thompson, a writer for Wired, are playing one of the games that von Ahn is developing called Matchin’. Two users at two opposite terminals (much like the Turing test participants) are shown matching pairs of pictures. They each select which one they find to be prettier. When they both select the same image, the selected image is marked as prettier and that data is stored away. After many plays, the data amounts to an objective, computational aesthetic judgment of beauty.
On their own, computers and A.I. cannot make these determinations. With the Matchin’ data, they can make them a priori, creating a program (or algorithm) with quantitative measurements corresponding to something like a(n) (human) aesthetic sensibility. Like the labor of reCAPTCHA, this is work of human computation: “the art of using massive groups of networked humans minds to solve problems that computers cannot.”
The goal of von Ahn is explicit. Thompson explains that he “wants to harvest every idle moment in our lives and turn it to productive use,” because if anyone, everyone, “could be coaxed into enjoying a game that contributed to solving a computing problem it would produce billions of man hours of labor each year.”  Let us note the procession of the various parts of speech: harvest, turn, use, coax, enjoy, contribute, solve, produce, idle, lives, game, computing, problem, billions, hours, labor.