MySpace is the most significant platform for social gaming besides Facebook, and the News Corp. company has just announced that it will add new language to its terms of use later this week that specifically prohibit “promotions that include hidden renewals without specific opt-in” features.

From the company’s statement today:

Principles and policies are nothing without action and we will continue to enforce our Terms of Use to put our users first.  If we find or are notified of violations of our Terms of Use we will contact the application developer and require that they modify their practices and adhere to our Terms.  If we do not receive a prompt and appropriate response we will, as we have in the past, remove the offending application from the MySpace platform.

What MySpace appears to be specifically targeting are the mobile quiz ads that have been included by many offer companies within offer walls inside of social games. As we reviewed months ago, these sorts of ads have kept popping up in within third-party advertising networks in social games on Facebook and MySpace (in fact, you’ll also sometimes see them in ad networks run by companies like Yahoo and Google).

Whether through an offer or another form of advertising, these ads eventually take users to an off-site landing page, where terms of the a mobile subscription are hidden by such mechanisms as making the terms the same color as the background page, or by slightly alternating the interface within a series of windows (see screenshots to observe the latter).

The user may think they’re entering their cell phone number to get the results of an IQ quiz or something, but in fact they’re signing up for an expensive subscription that will be billed to their phone account until they realize it and cancel it.

MySpace, like Facebook, already has policies against this sort of deceitful practice. But it is clarifying that no ad offers can run within social games or other apps that require a user to opt out of such a subscription, instead of explicitly asking them to opt in.

While these companies have been policing deceptive ads for months, enforcement efforts have picked up as evidence of these scams has been more heavily covered in the media in recent days. We still don’t know for certain the extent to which these scams have been running, but there have clearly been problems. Facebook, for example, issued some new policies in July, but increased enforcement last week, issuing social gaming companies and offer companies even sterner reminders of policies against deceptive ad practices. Since last week, these companies have been removing many of the mobile quiz ads, and other offenders. If social gaming and offer companies on MySpace haven’t already taken similar action already, then MySpace itself soon will.

[Images via VentureBeat]