There are a lot of people out there going about marketing on Facebook all wrong.
They will go to great lengths in filling out their profile, and not put any contact email there. If you are marketing, wouldn't you want people to be able to contact you?
Others never put anything on their profile except for a link to whatever they are promoting. This looks unprofessional and nobody is going to click that link.
The most common mistake though is flooding Facebook with your links in as many places as possible. You especially should not post promotional links on someone else wall or in a direct message at first contact.
Remember, it is called "Social" Media for a reason.