Brand marketers may ‘like’ Facebook, but the world’s largest social network has created numerous challenges. ROI is often hard to find; Facebook says it can take a year to produce. And despite the promise, certain kinds of initiatives may simply not work.

Now that it’s a publicly-traded company, Facebook is under even greater pressure to live up to its valuation, which currently reflects the fact that investors believe the social network has significant room to grow. To deliver the necessary growth, it has to find ways to convince marketers that it’s a productive marketing platform.

Unfortunately for everyone involved, that may not be easy, and it may create big headaches.

Case in point: Dan Wilkerson, a social media project manager at analytics consulting firm LunaMetrics raised some interesting questions about recent changes Facebook made to how it calculates its reach metric. Wilkerson explains that “As of July 3nd, Facebook’s reach metric will include both mobile views and will now only count a ‘reach’ if a user scrolls down and loads a Page’s story.”

The problem, as he sees it, is not the change itself, but what it implies about the accuracy and utility of the reach metric prior to July 3:

…it was always implied that each ‘reach’ point was a fan that had been exposed to your story at least once, just like the advertising parallel. However, according to the update, they apparently were counting reach as users who may or may not have seen your story, and were outright ignoring mobile exposures….This was a jaw-dropper for me. Over 500 million members of their user base access the service via mobile device, well over half their accounts. You mean to tell me that this entire time those views were unaccounted for in the reach figure?

Wilkerson makes the point that “without reliable metrics, we can’t make informed and strategic decisions” and given the nature of the changes Facebook has made, he believes historical reach data is essentially useless.

With Facebook change may be the only constant

Is he right? I’m sure there’s room for debate. But one thing is clear: marketers are going to need to accept that change is the only constant with the world’s largest social network. Need evidence of that? Beyond reach, there are other metrics-related changes Facebook has rolled out. In an AdAge piece, Dave Williams, CEO of Blinq Media, provides details:

With conversion tracking and analytics, advertisers can now specify a single action or multiple actions to be measured for any ad group, and can optimize to these metrics. For ads and sponsored stories pointing to internal Facebook pages, marketers can now track page Likes, page post Likes, comments, @ mentions, check-ins, photo tags, and page post shares (including shares of special offers from brands). Marketers can also track ‘claimed your offer,’ ‘answered your question,’ ‘clicked on the Page post link,’ ‘viewed the page post photo,’ ‘viewed the Page post video,’ and ‘viewed a tab on your Page.’

For ads and sponsored stories pointing to Facebook applications, this list includes installs, users, and the number of times Facebook credits were spent in the app. When it comes to Facebook’s events feature, they can track “yes” and “maybe” RSVPs. Marketers will be able to look at these metrics in 1-day view-through and 1-, 7-, and 28-day click-through attribution windows.

Williams largely seems to believe these changes are a step in the right direction, but acknowledges that they “are catching some advertisers and agencies off-guard.”

That, in the end, may hint at the biggest problem here: Facebook is running the measurement show and marketers are largely along for the ride. So long as marketers focus much of their investments on driving activity on Facebook (such as using Facebook ads to drive users to their Facebook Pages), they will largely be dependent on Facebook and its data to determine if those investments are paying off.

That data, as Wilkerson suggests, may not always be accurate, and even if it is, it’s worth keeping in mind that Facebook has every incentive to position activity on its social network in a positive light.

From this perspective, marketers should remember: Facebook can up the amount of measurement data it provides and create all sorts of new metrics for marketers to digest, but at the end of the day, when it comes to analytics, prolificacy of data and metrics should never be assumed to correlate with the productivity and profitability of a marketing campaign.