With Android being listed as the best-selling smartphone platform worldwide, it comes as no surprise that developers are flocking to its Android Market, which already has around 320,000 apps available as of September 2011 (374,303 as of Feb 5, 2012). A full 74 percent of those are free apps and while giving apps away doesn’t net a developer money off the bat, it’s still by far the best way for an app to become popular and gain traction in any app marketplace.

And after gaining a sizable audience, that’s the time you should think about earning from apps. The most popular way for monetizing free apps is by offering up ads. German research firm Xyologic released a report in mid-November that revealed the Android apps usage of mobile ad networks and presented these key findings:

• 50% of the top 1,000 downloaded apps on Android in October had at least one mobile ad or was part of an ad exchange network.
• 22% of the top 1,000 downloaded apps on Android in October had two or more mobile ads or were part of ad exchange networks.

So yeah, ads are really popular with free apps but there’s one big problem though: one-third of these apps are crap. What’s more alarming is that these “junk” apps are only made by a handful of developers: just 4.8 percent of the total number, in fact. The signal to noise ratio in the Android marketplace is pretty high and I’m sure you don’t want your app to be bundled into the “noise” category.

The thing is even though getting apps out there for free and just slapping them with ads seems like an easy way to make money, it’s not worth the effort. Earnings from ads is directly proportional to the amount of time a user spends on an app. For many free apps, users download them, use it a couple of times, and then forget about it. Low quality, ad-heavy apps suffer even a worse fate: users will open it, see that it’s really just spam then delete it. And if it really pisses them off, they’ll give it a low rating as well, which doesn’t help in attracting users one bit. It might be true that these apps are just there to earn a quick buck, but that’s all they will earn: a single quick buck.

Another reason why you should focus your energy into making your app better is that app marketplaces are wising up and starting to filter out copy cats, one-shots and intentionally deceptive apps that look like one app but really do something else. (Angry Birds lookalikes, anyone?) After all, if all you serve in your marketplace are crappy apps, pretty soon nobody will visit it. And yeah, you really don’t want to piss off Google; you don’t want to get banned after all.

The bright side is you really can earn from app development, if you do it right. The best way is to make your app really useful and to listen to your users. Case in point is the creator of APNDroid who even found out that some types of ads aren’t worth the trouble and relented by fixing it right away. Once users begin loving your app, they’ll have no problem with you putting in something that will help you earn from it. They also know that as long as a developer earns from an app this way, he or she has an incentive to make it better and provide support if needed. This leads to even more users flocking to it, starting a virtuous (and profitable) cycle.

We know that this tip is more of the general, Yoda-type of advice so we’d like to hear from you. What do you think would help in increasing the overall quality of Android apps available out there? Do you have any technical and design tips that would help apps stand out? What sort of things do app marketplaces need to prevent being flooded with these “junk” apps?