Screenshot by Donna Tam/CNET

Zynga users may have noticed something unfamiliar on the Web site -- Facebook ads have crept over to the gaming platform's site, filling the space that used to house Google ads.

The change was first noticed by Inside Facebook and it has the media speculating up a storm about whether this is the beginning of Facebook's advertising service empire.

Now when you connect with Facebook on Zynga.com, you'll see personalized ads and sponsored stories just like they appear in Facebook, the social network says. According to Facebook, you'll see only sponsored stores about activity that's been shared with you, and you can remove ads you don't like by clicking the X in the corner, in the same way that you can on Facebook. Also, Facebook won't share your information with advertisers, the company said.

Facebook has been building out its various advertising tools. It recently unveiled Facebook Exchange -- which creates targeted ads based on users' activity on the Web -- but swore that it wasn't an ad network. Facebook has not commented on whether it would be rolling ads out to other sites or if this is a Zynga-only endeavor.

But, as All Things D points out, a Zynga/Facebook advertising partnership isn't really a surprise. Zynga's S-1 filing last July noted a revenue sharing agreement where Facebook's ads would appear on Zynga properties.