Australians are becoming more guarded in what they share on their Facebook page as their lists of friends grows, according to local media agencies.

A monthly survey of 1000 Australians by WPP AUNZ has found anecdotal evidence that Facebook users are worried they may regret what they share in years to come, particularly as they are likely to now have hundreds of friends on the 12-year-old platform.

The news comes as analysts warn that regulatory uncertainty on privacy issues clouds the company's global ambitions even as it leads Google in online display revenue helped by its "unparalleled capabilities" to profile users and identify them across devices.

The increased reticence of Australian Facebook users to share personal information, which WPP has noticed since it began its FutureTrack survey in November, tallies with habits already noticed in the US, where Facebook is working to combat a decline in personal sharing, which is key to its attractiveness to advertisers.