Facebook's latest admission that it made a mistake in measuring advertising-related behavior on the site is a refreshing display of transparency, but it also happens to be the 10th time the company has made such an admission in less than a year.
The most recent screw up is a relatively minor one, and only affected a small number of advertisers and a tiny number of clicks. But that doesn't change the fact that it's the latest in a long line of similar errors, and that trend isn't helping the social network's pitch that it is the future of advertising.
In the most recent case, the company miscategorized certain kinds of clicks that were made by users interacting with ad-related video carousels on mobile devices. Even if someone just resized the carousel, Facebook defined some of those as clicks that took them to the advertiser's website.
Since advertisers typically pay more for clicks that bring a user to their site, this miscalculation resulted in some marketers paying more than they should have.
Facebook said the bug only affected 0.04% of all the ad impressions on the site, but nevertheless it is still issuing refunds to some advertisers who were affected, and promising that the problem has been fixed.
Get Data Sheet, Fortune’s technology newsletter.
The larger issue that arises from all of these mistakes is that advertisers are drawn to Facebook (fb) in part because their ads, and all the various ways in which users interact with them, can be measured in a thousand different ways. Using that data to target users and behavior more specifically is one of the site's key selling points.
To be told that this doesn't work sometimes isn't the kind of message advertisers want to hear, as they contemplate moving millions of dollars in ads from more traditional venues such as TV.
On top of that, the latest error comes right in the middle of the "Upfront" campaigns that cable networks and other media outlets are holding to try and woo advertisers, and one of their key messages is that the data coming from digital entities like Facebook can't be trusted. The most common criticism is that Facebook and Google "grade their own homework," as more than one ad manager has put it. In other words, they tell you what the metrics for your campaign are, but few are validated by any kind of third party.
In the NBCUniversal Upfront presentation on Tuesday, advertising head Linda Yaccarino scoffed at the idea of doing brand-awareness advertising on Facebook instead of on TV.
"What the hell is a view any way?" she asked the crowd of ad executives. "Has a 'like' ever walked into your store, purchased your product or drove a car out of the dealership?"
ESPN, meanwhile, made much of the fact that it is not only going to tell advertisers who watched their pitches via live-streams and in places like bars and restaurants, but all of this data will be verified by Nielsen, the leading TV audience-measurement company.
There are some in the TV business who are skeptical of Nielsen's ability to measure such things accurately, but at least the sports network is trying.
Facebook has also been making some moves towards soothing the advertising industry's concerns about the reliability of its measurement, especially after some of its more egregious errors, like the one where it said it over-estimated video views by as much as 80% for two years.
Among other things, the social network has expanded its third-party verification efforts to bring in more partnerships, including one with Nielsen and one with comScore.
After months of criticism, Facebook also recently agreed to have its advertising data audited by the Media Ratings Council, something a number of industry groups including the Association of National Advertisers had been asking for some time.