Since going public in what may be remembered as one of biggest IPO disasters ever, Facebook has come under fire as industry observers question the efficacy of its ad offerings.

But is all of the criticism of Facebook deserved? No, at least according to comScore.

Despite the fact that a large percentage of Facebook users say they’re ignoring Facebook ads, comScore says that it’s “time to change the discussion on measuring Facebook effectiveness.”

In a blog post last Thursday, it previewed some of its findings from its upcoming report, The Power of Like 2: How Social Marketing Works. comScore’s key claim: “Facebook earned media is having a statistically significant positive lift on people’s purchasing of a brand.”

It came to this conclusion through a “test vs. control methodology”, which the analytics firm believes is far superior to the surveys which have indicated most Facebook users are not paying attention to ads and marketing content on Facebook.

“While surveys can be useful in assessing ad effectiveness lifts across attitudinal dimensions such as brand awareness, favorability and purchase intent, people tend not to provide very accurate assessments of their own behavior. And their accuracy in recalling their own behavior over an extended period of time can be especially unreliable,” comScore’s Andrew Lipsman explained.

So do comScore’s findings, which will apparently cast a more positive light on Facebook, trump all of the evidence, some of it anecdotal, that Facebook just isn’t as powerful a marketing platform as many had hoped it would be? Perhaps, but there are a few key points worth keeping in mind:

  • comScore is not a disinterested observer. As AllThingsDigital’s Peter Kafka notes, Facebook is a comScore client and the two companies collaborated on this new report, as well as an earlier report on Facebook marketing. While it would be inappropriate to suggest that comScore and Facebook are cooking the books so to speak, there’s no doubt that with so much money being invested in social, companies in the online advertising ecosystem have little incentive to say “It just doesn’t work!”
  • There is no such thing as earned media on Facebook. comScore’s report focuses on ‘earned media’ on Facebook, but is there really such a thing? Brands invest a lot of money in their Facebook Pages, but they don’t really own them. Through its EdgeRank algorithm, Facebook can control the reach of brand messages, and when Facebook makes changes, those changes can have a huge impact — and not always for the better.
  • ROI may still be questionable. Even if there are ways marketers can use Facebook to positive effect, brands will still need to look at ROI. After all, ‘earned media’ on Facebook isn’t free. Case in point: of GM’s $30m in Facebook spend, $20m of it was apparently going to its ‘free’ Facebook Page. Clearly, content doesn’t create itself, and Facebook initiatives don’t run themselves.

At the end of the day, the differing views on the efficacy of marketing on Facebook serve as a strong reminder that there’s no substitute for defining, tracking and analyzing.

Facebook is changing, and will continue to change. Mobile usage is up, audience growth is slowing, and the company will continue to try new things. The only way brands can really make smart, well-informed strategic decisions around their Facebook marketing investments is to make sure they’ve defined KPIs for Facebook initiatives, are collecting the data needed to measure them and have staff diligently analyzing the data regularly to see if their investments are bearing fruit.

Brands doing anything less than this (like trusting a survey or a report) might as well flip a coin to answer the question, “Does Facebook marketing work?”