Updated w/ links below: Facebook admitted Wednesday to hiring Burson-Marsteller, which has drawn criticism after a potential op-ed source courted to knock Google published the PR firm’s overtures online.

USA Today this week said it was among “top-tier media outlets” targeted by B-M to place news stories and editorials about how Google’s Social Circle email feature violates the privacy of users.

Speculation broke out about who B-M was working for – the firm declined to say – but a Facebook spokesman confirmed to the Daily Beast that the social network hired the firm.

The spokesman said Facebook hired B-M because Google is moving into social networking services and also because Facebook “resents” Google’s attempts to use FB data in those services. The client and firm have since parted ways.

A Facebook spokesman later told the Wall Street Journal that the company didn't authorize or intend to run a "smear" campaign saying it hired B-M to "focus attention on this issue, using publicly available information that could be independently verified by any media organization or analyst."

The episode began when Burson reached out to blogger and privacy advocate Chris Soghoian to write an op-ed about Google’s service. When a Burson exec – former National Journal scribe John Mercurio -- declined to name its client, Soghoian posted his email exchanges with B-M online, sparking a spate of outrage over the common PR tactic.

B-M has called the situation “highly unusual” and said it does not represent standard practice at the firm.

“Whatever the rationale, this was not at all standard operating procedure and is against our policies, and the assignment on those terms should have been declined,” the firm said in a statement.

Facebook issued its own statement on the matter: ""No 'smear' campaign was authorized or intended. Instead, we wanted third parties to verify that people did not approve of the collection and use of information from their accounts on Facebook and other services for inclusion in Google Social Circles—just as Facebook did not approve of use or collection for this purpose.

"We engaged Burson-Marsteller to focus attention on this issue, using publicly available information that could be independently verified by any media organization or analyst. The issues are serious and we should have presented them in a serious and transparent way," said Facebook.

PRSA chair Rosanna Fiske, in a rare rebuke of a PR agency, criticized B-M for not revealing its client.

“Op-ed pieces are supposed to spring fresh from the minds of their writers, not be prompted by skullduggery,” blogged Pennsylvania PR pro Doug Bedell. “It's possible Mercurio might have disclosed his client to Soghoian later. But the damage in terms of the standards shown by this PR executive has already been done.”

Some other perspectives in the industry and media on the story:

"Shame on You, Burson-Marsteller" (David Reich)

"Do your actions pass the USA Today Test?" (Josh Morgan)

B-M deletes comments on FB page (Wired)

Facebook smeared Google? Come on! (@jackshafer)

Story source gives first interview (NYO's BetaBeat)

It isn't just right or wrong (@stuartbruce)

More to the story (@louhoffman)

Former Burson/U.K. chief: What on earth has happened to Burson-Marsteller? (@chelgate)

Kelly: It's incompetence more than malpractice (AW Page Society)

It's regular practice in PR (@text100)

Hyperbole meets hypocrisy: Googlegate (@jspepper)