Infecting People's Computers At fewer Costs

Research paper: "It’s All About The Benjamins: An empirical study on incentivizing users to ignore security advice, by Nicolas Christin, Serge Egelman, Timothy Vidas, and Jens Grossklags.

Abstract: We examine the cost for an attacker to pay users to execute arbitrary code -- potentially malware. We asked users at home to download and run an executable we wrote without being told what it did and without any way of knowing it was harmless. Each week, we increased the payment amount. Our goal was to examine whether users would ignore common security advice -- not to run untrusted executables­ -- if there was a direct incentive, and how much this incentive would need to be. We observed that for payments as low as $0.01, 22% of the people who viewed the task ultimately ran our executable. Once increased to $1.00, this proportion increased to 43%. We show that as the price increased, more and more users who understood the risks ultimately ran the code. We conclude that users are generally unopposed to running programs of unknown provenance, so long as their incentives exceed their inconvenience.

The experiment was run on Mechanical Turk, which means we don't know who these people were or even if they were sitting at computers owned (as opposed to, say, computers at an Internet cafe somewhere). But if you want to build a fair-trade botnet, this is a reasonable way to go about it.
Two articles.