If you're a writer and have even a smidgeon of online presence, you've probably been emailed or messaged or tweeted by Inkitt, a Berlin-based company that allows writers to post stories and get reader reviews and votes. A prolific spammer, Inkitt also conducts a lot of contests with titles like Vendetta Thriller/Adventure Contest, along with fanfic contests like Star Wars Sci-Fi Writing Contest (does George Lucas know?). Winning gets you badges on your profile page, and, occasionally, publication.
Tales of Inkitt spam can be seen here or here or here (I've gotten my share, as well). Vote-shilling by contest participants won a temporary ban on Inkitt posts on Reddit a few months ago.
Most recently, Inkitt launched its Grand Novel Contest (for which, no surprise, it is energetically spamming on Twitter):






