In addition to privacy issues, we want to give as little reason as possible for spammers to post links on Wikimedia sites and give them as little information as possible about how to design effective spam links. Providing data about the effectiveness of external links could benefit spammers.
There may be a way to make exceptions for providing aggregated data for a whitelist of GLAM links.
> Date: Sun, 23 Feb 2014 20:57:17 +0000
> From: Magnus Manske <magnusmanske@googlemail.com>
> To: "A mailing list for the Analytics Team at WMF and everybody who
> has an interest in Wikipedia and analytics."
> <analytics@lists.wikimedia.org>
> Cc: Strainu <strainu10@gmail.com>
> Subject: Re: [Analytics] [Wikitech-l] Exit stats?
> Message-ID:
> <CAGHUEtbjMyaT_c-FCxyOZsF9Bh0r8r7Mb3PwFmfO2T1NorhySg@mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> FWIW, I once had some JavaScript added to the common JS script on Commons,
> collecting anonymized clicks to external links on image pages, in an
> attempt to give some stats to the GLAM community. That would fire off basic
> data like time, page, and target URL to a toolserver logging script. Volume
> was low enough, but I had to turn it off due to privacy paranoia soon after.
>
> Cheers,
> Magnus
>