Fring is trialing something it should have implemented long ago if it ever planned on making money: ads.

Fring is essentially a mobile VoIP / chat service provider that works on the iPhone and any device running Windows Mobile or Symbian, with technology that enables users to make free calls using the Fring service itself, Skype, Live Messenger, Google Talk, and other communication services.

Up until now, the chat functionality was completely ad-free, but now Fring will gradually start rolling out banner display ads, beginning with a small number of randomly selected users.

From the Fring blog:

We wanted to give you the heads-up, as you may soon see small clickable advertising banners in the fring chat window, beneath the chat itself. Clicking the ad will open your browser and take you to the advertiser’s site; you may even find extra special offers, cool promos & other nice surprises behind the click from time to time And, more clicks mean happy advertisers; and happy advertisers mean more resources for us to develop cool new stuff for you to play with in fring!

The beta version of Fring was made publicly available in January 2007, and is now being used by millions of users across the globe. With (at least) $10 million in venture funding, the company was bound to come up with a monetization effort for all those users soon. Unlike competitors such as Jajah and Truphone, Fring is committed to keeping the costs of calling as low as possible and will try to make up for that revenue by slapping ads on chat screens.

(Thanks to Harel Schattenstein for the tip)