Post a boarding pass on Facebook, get your account stolen
Users often publish data that they don't know what they mean. Because at first sight, it's not possible to see what's the data, or what the data is for. Someone might find the data usefulf for something. In the worst case, it's possible to steal an account. Just be careful with the data you upload or publish. When you're not exactly sure what data is the in the picture or screenshot you want to upload to Facebook, you can just hide the data with a black rectangle or any other favorite shape (just blurring them might not be enough), or maybe just don't publish the data at all.