I found this news extremely distressing. From a cybernetic point of view, our phone is an extension of ourselves. It contains all the data we can't quite store in our own minds but being external to our bodies doesn't mean it's any more private than our very own thoughts. For example, we take photographs to remind ourselves of people or places or things, we take notes to augment our own mental notes. These are own private thoughts.
The fact that they are removing a variety of data without specific intent is paramount to mind invasion. The problem is, you aren't doing anything illegal now but who knows how the law will change in the next 20 years. You may WANT to do something legally wrong but not morally wrong and you are only as free as your right to revolt. This is one of those things that helps curtail that freedom.
Luckily there are many tools out there to help us evade such naivety. A tool such as Autowipe http://goo.gl/7u2GX will allow you to enter your phone password in wrong x times or else enter a specific password when they attempt to make you unlock your phone, this will cause the phone to completely wipe itself. As I haven't tried it myself I can't say how obvious the wipe is but either way your data will be safe from prying eyes.
Ultimately, the police are a collection of human beings and it is very difficult to stop that level of data theft being abused. For example, people ogling at naked pictures of girlfriends etc.. (not that I would be stupid enough to have something like that on my phone! but I am sure there are plenty of you out there).