We learned that what you post online will always be there and is easily accesible by the company that you work for. You can even delete them and you can still find them including their address and many other things you wouldn't think of.
3/4- you can find things online like a persons full name, address, phone number, job and where it is, how much they pay for taxes, what their house looks like. You can also find their relatives and if they are married or not. You can find any social networking