Straight from wikipedia -
http://en.wikipedia.org/wiki/ZyngaScam ads
Through 2009 Zynga made money from lead generation advertising schemes, whereby game participants would earn game points by signing up for featured credit cards or video-rental services. These were criticized as being less cost-effective than simply buying game points, and in some cases, being outright scams that would download unwanted software or unwittingly sign up for a recurring subscription.[38] One ad signed up players for subscriptions to expensive and unwanted text-messaging services.[39]
On October 31, 2009, Michael Arrington of TechCrunch said that Zynga intentionally worked with scam advertisers, and that lead generation made up a third of Zynga's revenue.[64] Arrington also alleged that Facebook was complicit in this.[65] On November 2, 2009, CEO Mark Pincus announced a reform in its offers: Tatto Media, a major offer provider that enrolled users into recurring cell phone subscriptions, would be banned, all mobile offers would be removed, and offer providers would be required to pre-screen offers.[66]
Arrington continued to question Pincus' role in the scams, republishing a video of a speech by Pincus.[67] In the speech, Pincus said:
"So I funded [Zynga] myself but I did every horrible thing in the book to, just to get revenues right away. I mean we gave our users poker chips if they downloaded this Zwinky toolbar which was like, I don't know, I downloaded it once and couldn’t get rid of it. laughs We did anything possible just to just get revenues so that we could grow and be a real business." —Mark Pincus, Speech from Startup@Berkeley
In response, Pincus noted that after offering the Zwinky toolbar, his team of ten decided to remove it since it was a "painful experience".[68]
Several days after the Techcrunch story, Zynga's most recent Facebook game FishVille, was temporarily taken offline by Facebook on claim of advertising violations. According to Zynga, Fishville had 875,000 users within two days of launch. A release from Facebook on its reasons for taking the game offline read that "FishVille will remain suspended until Facebook is satisfied that Zynga demonstrates compliance with Facebook restrictions – as well as Zynga’s own restrictions – on the ads it offers users."[69] FishVille was later un-suspended at midnight November 9–10.[70]
Several suits were filed against Zynga for promoting such offers,[71][72] including the class-action lawsuit Swift v. Zynga in the United States District Court for the Northern District of California for violation of the Unfair competition law and the Consumers Legal Remedies Act, after the lead plaintiff's credit card was billed more than $200 for offers she completed to receive YoVille currency.[73][74][75]
Pincus later said that he had been too eager to increase company revenues through advertising, and that operating in reactive mode by taking down ads only after receiving complaints had not worked. The company removed all ads for a time, relying only on direct purchase of game currency, then began reintroducing third party ads only after they had been screened.[38]