App permissions seem to be completely coarse-grained, and they all seem to need access to potentially huge amounts of personal data. I can't, so far as I know, disable their access to specific bits of data I don't want them to have; nor do I know of any mechanism for blacklisting or whitelisting access to specific internet hosts.
My Moto X decided a while back that it wanted to upgrade itself and started bringing up a nag screen at frequent intervals, interrupting whatever I was doing. There is no way I can discover to turn this off, and there is no way to decline the upgrade. It just kept nagging me, many times a day, for months. I can't disable this behavior; I can only choose between reduced functionality (getting interrupted mid-sentence and having to dismiss a dialog many times a day) or letting this remote server take over and install its software on my hardware.
In the end I feel like this device doesn't actually belong to me at all. It's more like a rental apartment: I can use it, and I can keep my stuff in it if I want to, but ultimately it belongs to the landlord; which in this case is a combination of Google, Motorola, and T-Mobile. The deal seems pretty clear: they get to decide what I am allowed to do with my phone, they get to decide where my information goes and who gets to see it, and I can either accept the deal or not use the phone. For the most part I have chosen the latter.