This according to researchers at NYU. They investigated all new HIT requesters on Amazon's Mechanical Turk site for September and October (Mechanical Turk is an Amazon site where people can perform small tasks and get paid, HIT is the term for those tasks).
Anyone who frequents just a little bit the market will notice the tremendous number of spammy HITs. (HIT = a task posted for completion in the market; stands for Human Intelligence Task). "Test if the ads in my website work". "Create a Twitter account and follow me". "Like my YouTube video". "Download this app". "Write a positive review on Yelp". A seemingly endless amount of spam HITs come to the market, mainly with the purpose of spamming "social media" metrics.
The results were grim as 40.92% of the tasks were designed around sending spam, generating false metrics, or sometimes going to a site and giving your personal information to "test" a data entry form.