Facebook this week announced a long-awaited feature that will allow users to disconnect their account from their app and website history, which would disable Facebook from using that information to target ads at them. But one analyst is saying that the feature falls short of Facebook's original promise, while Facebook disputes it.

SunTrust Robinson Humphrey analysts said in a research note the "Off-Facebook Activity" feature "appears to fall somewhat short of the original pledge by CEO Zuckerberg of empowering users to 'flush their history whenever they want,' and delete all the relevant data." Analysts remarked that "data is disconnected but not deleted," and would remain on Facebook's servers for a length of time that isn't clear.

A Facebook spokesman said the feature is consistent with what the company originally announced. In a post last year describing the change, Facebook said the feature would allow users to see websites and apps that send information when they use it, delete that information from their account and turn off Facebook's ability to store it with their account going forward.

The distinction seems to be that Facebook is deleting this kind of information "from the account" — but not altogether. Facebook will still have data about interactions (like opening an app, adding an item to a shopping cart, searching for an item or making a purchase), but claims that data wouldn't be connected to individual users if they chose to opt out. Facebook still can use the data for analytics reports, or to provide advertisers with some basic information, like whether an anonymous user made a purchase after they viewed an ad.

Facebook, on the "disconnect" versus "delete" question, said on its website that the information would no longer be connected to a person's profile. "This data can still be used without being linked to an individual user to allow us to let businesses know how their website, app or ads are performing," Facebook says.

Like other onlookers, SunTrust analysts believe that the feature being "opt out" means it likely won't be widely adopted.

"Requiring users to go through settings options to make changes to their privacy likely increases friction enough to discourage and limit mass adoption of the new tool, in our view," they wrote.

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