From the projects website [1]
> libgdata is a GLib-based library for accessing online service APIs using the GData protocol — most notably, Google's services. It provides APIs to access the common Google services, and has full asynchronous support.

libgadata is in @your-privacy-blacklist.txt@ (formerly known as @your-coherance-blacklist.txt@) since commit 518631a55982f42e28bd4342d9354cd07463d57f [2].
The mentioned reason in the package:
> provides support for unsafe and dangerous for privacy services

I tried to find some security issues related to it, but the ones I found (such as [3]) were closed before libgdata was blacklisted.
I looked also at parabola's mailing list at that time, but could not find more informations.
Probably the reason for blacklisting it _is_ the google dependency. I think this could be a good moment to re-evaluate libgdata and (at least) clearly state why it is blacklisted.

Packages that depend on libgdata and are blacklisted today:



| Package | Replacement in [nonprism] | Rationale Notes |
| claws-mail | x | optional depends of libgdata |
| eog-plugins | x | depends of libgdata |
| evolution-data-server | x | depends of libgdata |
| gnome-documents | | depends of libgdata |
| gnome-online-miners | | only useful with libgdata (provides provides support for Facebook, Flickr, Google and SkyDrive) SkyDrive |
| gnome-photos | | depends of libgdata and gnome-online-miners |
| grilo-plugins | x | optional depends of libgdata |
| libgdata | | provides support for unsafe and dangerous for privacy services |
| shotwell | | depends of libgdata and contains support for Facebook, Flickr, Picasa, Tumblr, Yandex and Youtube (Note: Youtube option has support for registered users only) |



[1]: https://wiki.gnome.org/Projects/libgdata
[2]: https://git.parabola.nu/abslibre/blacklist.git/commit/?id=518631a55982f42e28bd4342d9354cd07463d57f
[3]: https://seclists.org/fulldisclosure/2012/Jun/18