I don't think you are understanding what you are quoting here. They are referring to public communications posted to a forum. If I put my email address in this reply that I am typing to you, it's available to the whole wide world. Not only can any forum user now know my email address, but there are folks that use software to "scrape" such data from public forums.
This is no different than using FaceBook. IF you post your bank account number on your face book wall, you have just made it public to the entire world.
This statement is just warning you to be careful not to post data to a forum or a feature request submission or the like that you don't want the whole world to see.
This has nothing to do with the security of data within FileMaker Pro--something that is the responsibility of each database developer and database manager (and any IT department so involved) to protect.