Facebook delivered some good news this week: its active users' total roll is nearing the one billion mark, specifically some 955 million members worldwide as of the end of June 2012, in the process proving the wide-reach of the hugely popular social networking site.

However, the recently public company admitted too that about 83 million accounts currently hosted on servers could be considered as 'dodgy' - meaning these 'personal pages' were either mirror accounts by existing users or were simply set up to serve other purposes that Facebook labelled as dubious.

On its latest filings with U.S. regulators, Facebook said some 8.7 per cent of its total user accounts can be considered as 'garbage space' since it is likely that they were created to capitalise on the company's global reach or users would simply want to maintain more than one account in recording their online footprints.

From the sham pages, 2.4 per cent were presently circulating on the web to promote business interests or show off people's love for their cats and dogs, Facebook said.

Most likely, the same accounts can be used to fire off unwanted and unsolicited messages or adverts, the company added.

The internet giant also pointed to duplicate accounts, which it estimated to comprise some 4.8 per cent of its active users, as another source of concern.

Phony accounts, in fact, were major headache for Facebook as it generates majority of its revenues form advertising dollars and with too many of them, companies may find it too hard to believe that their promotional thrust on the social media firm was worth the trouble, analysts said.

"Companies who are considering advertising on the social network want to be sure that any 'likes' they receive are from genuine users, not bogus accounts," security analyst Graham Cluley of UK-based Sophos told Agence France Presse (AFP) on Wednesday.

The high number of illegitimate accounts that Facebook seems unable to effectively crackdown could also alert serious members on the social networking site's vulnerability.

Facebook itself has admitted that duplicate and questionable accounts on its servers could be employed to spread out spasm or carry out malicious intents.

Their presence, the company conceded, serves as "inherent challenges ... despite our efforts to detect and suppress such behaviour."

But Facebook insisted that something concrete is now underway to address the issue, which it deems with grave concerns.

"We are continually seeking to improve our ability to identify duplicate or false accounts and estimate the total number of such accounts, and such estimates may be affected by improvements or changes in our methodology," AFP reported the social media giant as saying on its filings before the U.S. Securities and Exchange Commission (SEC).

Currently, the level of concern is more worrisome in emerging markets as Facebook hinted that users located in areas like Australia and the United States were not giving too much problems to the company.

Facebook has issued the report as it fends off growing unease over its market viability following the steady retreats of its stock values since the company went public on May this year.

From its initial offering of $US38 per share, Facebook saw its shares suffering steep declines of more than 45 percent though the current week's trading.

Media reports said the slides since two months ago have also eaten up some $US7 billion from the personal holdings to the company of Facebook co-founder and CEO Mark Zuckerberg.