Ads in smartphone apps are already annoying, but did they have to go and put them on your lockscreen too? It looks like some developers may have pushed their luck; Google has updated its Policy Center to explicitly call out -- and prohibit -- apps from showing advertising on Android lockscreens.
Google's Developer Policy Center does a good job of not only describing, but showing what sort of advertising is not OK. A new section has appeared on the page, specifically targeting everyone's new favourite ad type:
Lockscreen Monetization Unless the exclusive purpose of the app is that of a lockscreen, apps may not introduce ads or features that monetize the locked display of a device.
The succinct rule leaves a little wriggle room for lockscreen apps themselves, but for everything else, it's now a no-go zone.
Hopefully Google will be proactive in removing apps that go against this policy, but at the very least, it should significantly curtail the appearance of new apps and updates that try to cash in on your lockscreen.