As Microsoft pushed Outlook.com out of preview mode today, analysts said the company's "Scroogled" attack ads, which fired shots at Google's Gmail two weeks ago, were effective.

"We all like to think that we don't like attack ads, but the fact is, they work," said Peter LaMotte, an analyst with Levick, a Washington-based strategic communications consultancy.

Microsoft has collected less than 10,000 signatures on its anti-Gmail petition, part of its advocacy approach in the latest "Scroogled" campaign.

Today, Microsoft removed the "preview" label from Outlook.com, the company's hope for reclaiming the top spot in the free email service wars. Microsoft is supporting the rebranding effort -- Outlook.com was formerly Hotmail, a nameplate that harks back to 1996 -- with an online and television advertising campaign.

But two weeks ago, Microsoft reopened its Scroogled attack ad campaign against Google, blasting Gmail and its machine-reading of email messages to display ads. The Scroogled campaign debuted in November 2012, then targeting Google's search practices.

LaMotte, a former ad executive and currently the leader of Levick's digital team, cited last year's groundbreaking real-time surveys of political ads by Vanderbilt University in conjunction with You.gov to support his thesis that attack ads work. Those surveys found that while Americans decried negative political ads, those advertisements were often the most memorable, and presumably the most effective.

Microsoft was roundly criticized by bloggers and pundits for the "Don't Get Scroogled by Gmail" campaign that launched Feb. 7. Todd Bishop, who writes the popular GeekWire blog, asked "Aren't we smarter than this?" Meanwhile, Techcrunch asked, "Why so negative, Microsoft?"

But some saw the campaign as hitting its target, negative be damned.

"I think this is an effective attack," said Ezra Gottheil, an analyst with Technology Business Research, in an email. "I've come to terms with Google's software reading my mail, but it definitely creeps some people out. [And] Gmail is a real threat to Outlook. It is already eating into Outlook's market share, so why not fight back with what you can?"

In October 2012, metrics firm comScore moved Gmail into first place, worldwide, when measured by unique visitors, unseating longtime leader Hotmail.

"And as the Godfather said, this is business," Gottheil said. "Not that companies do not act out of animosity, but this makes sense as a cold-blooded business decision."

But what was interesting about Scroogled was not its attack-dog tone, LaMotte said, but how Microsoft constructed the campaign. "It's really taken an approach more in line with political advocacy campaigns, and under the guidance of Mark Penn, is using the guise of advocacy," he said.

Penn, a longtime political and media strategist who worked as an adviser to former President Bill Clinton during his administration and on Hillary Clinton's 2008 presidential campaign, was hired by Microsoft in mid-2012 to head a strategic special projects group. Penn, who has consulted with Microsoft since 1998, has been credited with creating Scroogled.

"This is more than just an ad. This is a fully realized advocacy campaign," LaMotte said.

Those kinds of campaigns, often run by environmentalists and groups that advocate changes to state and federal constitutions, are characterized not only by advertising, but also by partisan-funded research and grassroots components like petitions.