Google recently announced that in Android L encryption would be turned on by default:
For over three years Android has offered encryption, and keys are not stored off of the device, so they cannot be shared with law enforcement. As part of our next Android release, encryption will be enabled by default out of the box, so you won't even have to think about turning it on. (Reported by The Washington Post 18-Sep-2014.)
Currently, if I have an Android phone and I have a Google account associated with that phone, if I forget my phone's PIN I can still get by using my Google account credentials, at least according to Recover Android Device in case of Forgot password/pattern unlock an Android device.
How does turning on encryption by default help protect against law enforcement accessing the device's data if law enforcement can go to Google and get them to reset the user's Google account credentials and thereby get around the PIN? (Let's assume that the device we are considering has a PIN and a Google account associated with it.)