Many of the recent generations of cameras, Iphone's and Android devices have built in GPS. When you take a picture using any device with GPS enabled, the lat-lon coordinates are included with the EXIF data that is a part of the image file and is quite easy to read.
In other words, when you take a shot of your stash on your kitchen table and post it on the internet, your your home address is encoded along with it. There are many free EXIF data strippers.
Just be aware.
(tip originated with SilverStackers)