If petrol is the fuel of the brick and mortar economy, ads are the fuel of the internet economy. In the world of Android (News - Alert) apps, ads range anywhere from being relatively innocuous to wretchedly irritating. Anyone who doesn't like ordering “pro” versions of apps is familiar with these pesky little creatures.

Gmail is one of the most used apps in the Android ecosystem, and it's been relatively ad-free since it's existed. The latest versions demonstrate the talent that Google (News - Alert) has in making interfaces that are simple, but elegant and intuitive.

Gmail's web client had ads since as far as anyone can remember, and they've been generally uninvasive. There had to be a point in time, eventually, when Google will want to capitalize on its Android users. Today, it's no longer a question of “if” and more a question of “when.” It seems that the time has come for Gmail to start showing ads in Android, according to the latest APK teardown by Android Police done on Saturday.

Android Police has discovered a new library called “ads” in the app, and has also found hints to an interface feature where users can save ads that they like (presumably so that Google can construct an advertising model that caters to each individual user).

There are still many questions unanswered, though. How large will the ads be? Will they be invasive, or will they almost blend with the rest of the interface as they do with Gmail? Will Google be expanding this onto other products, such as Google Drive?

Only time will give us the answers to all of these questions. For now, let's just enjoy what seems like the last few days we'll actually see Gmail without any ads. Who knows? Maybe we'll come to actually like the advertising model.