Lot of persons having fake account with facebook, as fb allow us to create a lot of accounts using the same ip. Some people using this facility and creating a fb account for their various emails. There is nothing wrong if we don't use this kind of fake account for illegal purpose, but some persons creating fake accounts to do some unwanted activities in fb. So we must be very careful while dealing with fb. Don't believe all the fb profiles, some of them are fake and created for some business purpose and other issues.
Marketers and business persons are interestedin buying fb account with lot of friends to send their marketing and business mails, so some people are interested in making this kind of fake accounts with facebook and adding a lot of friends in their fake id and sell their account after
Now a days lot of people are interested in making money with their fb account and creating this kind of fake accounts and selling it to the marketers to earn more from it. This kind of fake profiles are quite common in fb now. Don't accept the friend request from a strange person or unknown application if you suspect them a lot. It is very hard to guess about a person with their fb profile, because most of them are using fake profiles in that site.