Federal agencies in the US have reportedly been given access to users accounts by Facebook several times without informing the users.
According to a Reuters report, since 2008, federal judges have authorised over 20 warrants to search Facebook accounts of suspects.
Reuters reported that its review of the Westlaw legal database shows that the warrants requested personal data such as messages, status updates, links to videos and photographs, calendars of future and past events, "Wall postings" and "rejected Friend requests."
However, none of those warrants have been challenged for breach of personal privacy. It is also not illegal for neither agencies nor Facebook to keep such investigations secret from the users.
The suspects against whom the warrants were issued by federal agencies such as the FBI, DEA and ICE were being investigated for a range of crimes from arson to rape to terrorism, said the report.
Recently, microblogging site Twitter had announced that it would hand over user information to authorities if required but would first inform the user about it.
Facebook has not said whether it had a similar policy or not.
