(called Skrill today). This helps explains why the author of this paper and possibly other non-US-based researchers first discovered microworkers. Works by @Gardlo2012 and @Crone2017 aimed to assess the usefulness of the platform for scientific purposes; and indeed, scientific projects regularly, though relatively infrequently, appeared on the platform. However, it is possible that this difference in payment methods is only one of the reasons behind the nature of the campaigns conducted on each.

Hirth et al.’s work [@Hirth2011] indicated that gray promotional campaigns were already existed as long ago as 2011: “Signup”, “Click or Search”, “Voting and Rating” were already featured as campaign categories; however, the payments offered were slightly higher than today.

The connection between social media and marketing was analyzed by @Thackeray2008 as early as 2008. Of course this work concentrated on the legitimate social media strategies firms might embrace, such as paid search results, where the brand buys a presence in the search results. As @Yang2010 explained, these are usually placed in a separate area on the results page, together with being clearly to indicate that they are paid for or they may be labeled as an ad, e.g., on Facebook (the difference between “paid” and “organic” 