Google has placed its user data off-limits to Facebook, in another sign of rising conflict between the search heavyweight and the social network.
Until now, Facebook has used Google Gmail addresses to help users locate friends who are already Facebook users.
However, Google said it would block Facebook from importing its users’ contacts because the social site did not reciprocate.
“We have decided to change our approach slightly to reflect the fact that users often aren't aware that once they have imported their contacts into sites like Facebook, they are effectively trapped," Google said in a statement emailed to US media.
“We will no longer allow websites to automate the import of users' Google Contacts unless they allow similar export to other sites,” Google said.
Wired reports that Facebook generally doesn’t reciprocate in offering user data to other services “unless they are partners.“
“If you are also a Twitter or Buzz user and want to find out which of your Facebook friends were using those services, Facebook will not let you.
“Google — which has plenty of reasons to covet the rich mine of user data hidden behind Facebook’s walls — simply had enough.”
The search firm is also clearly worried about the growing competitive threat from Facebook.
Its own social network efforts, such as Orkut, the recently-closed Wave and Buzz – which just paid out $8.5 million to settle a privacy suit – have not moved the needle.
Gartner analyst Ray Valdes told Reuters that every time that Facebook users use the social site’s email or instant messaging or search, they “will chip away at Google's properties.”