If two devices create valid transactions on two independent subtangles and the system tries to reconcile these tangles into the main tangle afterwards, how do they determine which transaction is valid?
The subtangle with the highest weight.
when you start thinking about possible applications it's actually quite hard to come up with something that seems both interesting and doable.
I can think of a number of niche examples that would benefit from both data security and a value settlement layer
no one seems to think about the privacy implications of having IoT data
This is constantly being thought about. GDPR compliance is quite a tricky one, then you have Japan which even classifies the hash of personal data controlled. This doesn't mean its being left behind.