Be it anything, has two sides of coin. Likewise Facebook has few advantages and disadvantages.
Advantages :
Facebook is used as social media or network to stay connected with family, friends, office collegues and new people.
Facebook is used for business. Company profiles can be created on Facebook and used to share the links. More the publicity more the chances to get orders as people get to know about your company.
Facebook is used to share information and news. Now a days people just share every thing happens in personal life as well.
Facebook can be used as personal portfolio. It would help you to make your profile and skills to be known by the public and companies.
Disadvantages :
Students are getting Facebook addicted & they keep themselves away from real society but it may not be as such disadvantage as people has to think by themselves how much time they should give for social media networking.
Misuse of girls profile pictures is another issue.