SwiftKey, makers of a third party keyboard for Android, joined up with two technology publications to survey over 17,000 smartphones users about the number of paid applications they have on their devices. Back in 2011, 12% of Android owners said they had zero paid apps on their phone. Only 10% had 20 or more paid apps. This year, those figures are now 7% and 19% respectively. Translation: Android users are slowly becoming more willing to pay for apps, but if any serious money is to be made here then you’re going to have to make free apps that are ad supported.

Which android network you decide to go with will make or break your bottom line.

AppBrain, a curator of Android applications and creators of the AppLift ad network, recently analyzed about 60,000 apps that were removed from the Google Play Store to see why they were given the boot. Their findings suggest that going with ad networks such as StartApp, TapJoy, AirPush, and other networks that make aggressive use of push technology in order to get a user’s attention, results in customers giving apps poor ratings.

Why now? Google changed their policies regarding submitting apps to the Google Play Store on August, 30th. They’re trying to keep application that are “spammy” out of their ecosystem to protect users.

The good news for developers is that the number of new apps submitted to the Google Play Store that use such shady monetization techniques measures below 20%. If you’re going to build an ad supported free app, and chances are that you will since that seems to attract the most number of users, AppBrain’s data suggests you go with one of three ad networks: Admob (which is owned by Google), Millennial Media, and InMobi.

At the end of the day, the old adage remains true that advertisements have to be relevant to your users if you want them to click, or in this case touch, them.