The popular VOIP service Skype will start displaying advertising in its Home tab beginning this week.

The company has just announced the change, insisting that, "the Skype experience is our first priority." The move to bring advertising to the Skype environment comes as the telephony company makes its move for a planned IPO this year. While Skype has an estimated 177 million active users, only around 8.1 million are paying subscribers. The addition of advertising will give the company another revenue stream.

"We think this is an interesting opportunity for advertisers," says Doug Bewsher, Skype's chief marketing officer in an interview in Ad Age. "This is a premium placement to engage with our users." Indeed, people spend a lot of time on sites like Skype, and while Bewsher notes that ads on other social networking sites like Facebook can be small and unobtrusive, ads in Skype may offer more user engagement - "click to call," perhaps.

Currently, the advertising is set to only appear in the Home tab in Skype for Windows, although the company says it might experiment with ads in other areas and with other clients eventually. The ads won't interrupt your VOIP experience - no "annoying pop-up ads or flashy banner ads in middle of conversations," insists Skype. Skype says the ads will only appear occasionally, and the initial plan is to show one ad from one brand per day. Ads are rolling out in the U.S., U.K., and German markets first.

The advertising may use non-personally identifiable demographic data - your location, gender and age - in order to target ads and deliver relevant content. But you will be able to opt out of allowing Skype to share this data with advertisers.

Skype has become immensely popular, in no small part because it's offered its services for free. As Skype moves towards its initial public offering, ads appear to be one path to monetize those users.