In recent months Facebook has been accused of allowing private messages to be made public in their new 'timeline' feature - an allegation they have strongly denied.
According to the Daily Mail, users' private information is valuable to companies wanting to advertise to audiences.
Bulgairan Bogomil Shopov, a blogger and digital-rights activist, claimed that he was able to buy data containing names, user IDs and email addresses.
He also alleged that Facebook later asked him to delete his post detailing the purchase, the report said.
Shopov claimed that he bought the data from a user called 'Mertem' on digital odd-jobs board Gigbucks, where users offer to perform tasks in exchange for payments between five and 50 dollars.