Yeah I've seen things like this before. The problem is that any app could register to listen to those addresses, and that opens up an avenue for mis-leading the user. I'm sure Google would not like it if the Bing app started trying to become the handler for google.com URLs. Likewise on iOS anybody can submit an app which listens to the fb:// URL. Overall it seems unsafe.
It's actually pretty common in Android. Methinks you're an iOS user :)
> any app could register to listen to those addresses
This is core to the Android IPC design. Apps/Activities describe what they can handle (Intents, actions, filters), and I think it works pretty well. Android will ask you if you want the given app to be the default or not, and you can always un-set the default. Also, if you have a new app that can handle the given link, the next time you try to launch that link you'll be prompted to see if you want to use the new app, and your previous selected default will be highlighted as a reminder.
Also, I'm generally a believer that if an app is registering for an Intent action filter that it does not handle well/shouldn't handle at all, then users will give it a lot of bad review feedback, and apps will trend towards doing the right thing.
> The problem is that any app could register to listen to those addresses
That's a feature, not a problem, and it's the kind of flexibility I expect from Android.
Take the domain reddit.com, for example. There are several Reddit apps, two or three of which are very popular. If the app to open was controlled by the owners of reddit.com, how would my favourite third-party app be able to register to handle those links?
Android already handles this. You get a popup box listing all of the apps that can handle a particular URL. You can choose whether to use that app just this time or to set it as default and not ask again. Defaults can be cleared in the system settings.
