I don't know if this can happen of course, but when using signed message to prove that you own something else than address, i saw some people doing that. So they could lie that they own something else while they don't?
They can write whatever they want. A signed message can not proof the message itself is true, it can only show you that its still the same person you trusted 2 years ago. Well, unless that person sold the private key to the address. Its not the holy grail of establishing trust, it can just be a piece in a bigger picture.
You can find the most of the answer in shorena's thread. https://bitcointalk.org/index.php?topic=990345
The uses and with that you will be able to know how people can use it.
Are you posting only to have 1 more post for signature campaign? Because if you would have read past messages of some users you would see that one sent me this link
