A media lawyer is warning that the Advertising Standards Board's ruling on Smirnoff's Facebook page will put the onus back on companies to be more vigilant about the nature of the comments people are posting to their company pages.

Large advertisers such as Qantas, Telstra and Coles are increasingly reliant on their Facebook pages to get consumers to ''like'' them and get free referrals to their network of friends.

John Swinson, a partner at law firm King & Wood Mallesons, said the board's ruling "turned people's opinions into statements of facts".

Mr Swinson said that if, for example, a member of the public posted a comment on Smirnoff's site that claimed it was the purest Russian vodka and would lead to success with the opposite sex and Smirnoff failed to remove it, the company could be liable on a number of counts.

"Smirnoff is Australian not Russian. So that is false. It may not be the purest so that could also be misleading.