Staff were running personal apps on company phones and copying sensitive client email across into personal accounts. Nobody could reliably detect it happening and nobody could prove it afterwards.
We put application protection policies in place that govern the corporate data and nothing else. People keep their own apps, but work email can no longer be copied or forwarded into a personal account, and the corporate side can be wiped on its own whenever it needs to be.
The leakage stopped completely, and staff satisfaction scores did not move