A number of tech sites noted last week that Facebook had introduced a slightly redesigned version of its well known icon. The light blue rectangle that hinted at a horizon is gone. The arms of the F have been slightly altered.
The icon redesign is part of a larger effort to streamline the icons used by various corporate divisions. The generic icons for entities such as "Facebook Developers" and the special pages for politics, universities and non-profits have been replaced by simple blue squares with white images on them.
So far, Facebook doesn't seem to have made any statements about the new icons, and they are probably indulging the relatively massive media attention they get for such subtle design changes. It seems the icons were uploaded around April 11-12.
These are some of the new icons:
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