I was thinking glorified bookmarks at the beginning too, but then I saw how it integrated the last.fm controls into the media widget in the panel. I am also currently using the Online Accounts functionality in Gnome, and it is pretty cool how it will automatically use the credentials from each account I specify in applications which support it.

My main use case is my multiple Google accounts (work, uni, personal) and their respective calendars. I just fire up evolution, it automatically connects to Google and the calendar widget in the panel populates with my events. Its just a shame that only evolution does this, and Thunderbird does not seem to integrate with it.

This is pretty similar to Android, how you specify your online accounts, and it is up to individual applications to make use of those credentials if they please. There just seems to be much more usage of this in Android than in Gnome.

Gmail and Google+ came up under the communications menu, and last.fm was integrated with the sound menu. App menus and features seem to be available from the HUD. Seems pretty well integrated to me.