Google said it took down over 700,000 apps from its Play store in 2017 becasue they violated its policies, and that was 70% more than in 2016.
It says it's using machine learning to help stop apps before anyone could download them.

It also says it took action against 100,000 bad developers in 2017.

It just goes to show the scale of the problem faced by intermediaries, such as Google's Play store, and ultimately, end users.
One thing it indicates to me is that it's far safer to download from the Play store than to download off the Net.

[android-developers.googleblog.com...]