In the rare event that you need to take a picture of a piece of mail, it's common practice to censor your address. Be sure to block out the barcode as well.
Picture: Marit & Toomas Hinnosaar
Printed envelopes with your address on them will often include a barcode similar to the one in the photo above. These codes typically include your address in its entirety. In some cases, they can be read easily. mailScan is an app for Android that reads these IMB (Intelligent Mail Barcode) codes and returns the information stored. It doesn't work on all codes, but it works on enough for it to be a concern.
Of course, if you want to censor information in a photograph, remember that blurring it may not be the best idea. In some cases, particularly when it comes to barcodes and other printed information, it can be possible to reverse a blur effect. Blocking it out with a solid colour is much more effective. Alternatively, avoid taking pictures of your mail altogether.