Social game developer Zynga (FarmVille, Mafia Wars) announced it is discontinuing all of its performance-based Facebook advertising until further notice, after taking fire for tactics that have users receive in-game currency in return for signing up for offers that often turn out to cost more than expected.

The company's decision was more than likely spurred by Facebook's temporary removal of its new FishVille game last weekend due to potentially confusing mobile subscription ads that showed up, which the social network prohibits.

TechCrunch's Michael Arrington explained that: "These ads clearly violate Facebook’s terms and conditions. They don’t state on the offer page that the user is required to enter into a $10 – $20/month mobile subscription, and there is no opt in by the user before entering in personal information."

Though FishVille was launched only two days prior to its suspension, the game had already attracted more than 875,000 users.

Zynga, which previously vowed to remove the mobile ads from its offers, claims the promotions showed up because of a technical glitch with its offer provider, and says that the mobile ads only appeared with 10 percent of pageviews.

CEO Mark Pincus admitted in a post on his weblog, "Zynga has not been able to control the ad content as it is managed by the offer companies that we work with."

"We recognize it is our responsibility to ensure that offers which generate a bad user experience are not shown with any of our games," he continued. "Therefore, we are removing all CPA [cost-per-action] offers across Zynga games until we can control their inclusion and presentation ourselves. ...This move is worth it for the long-term user experience and value to our partners like Facebook and MySpace."

The developer's move to take out its CPA ads will come at no small cost, as those ads reportedly account for a third of Zynga's total revenues -- though Pincus said it's significantly less, claiming yesterday that the lead generation offers actually made up less than 20 percent of the company's revenues. Zynga believes it needs to have complete control over the offer approval process before it can commit to 100 percent compliance.

"Currently no partner offers a work flow that we can be completely confident in and that is why we chose to remove the offers till we can put it in place," said Pincus in an email to VentureBeat. "We do not have an estimate as to when that will happen but are working with our partners to insure a superior user experience where our users can avail themselves of high quality offers, each of which has been vetted by us for compliance and quality."