Facebook and Twitter Log In Screens: Separated at Birth?

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Twitter's new log in screen shows a strong resemblance to Facebook's.  The layout is virtually the same, a diagram of the world appears in both, the slogans sound similar and are positioned in the same place, the language links are both at the bottom, etc.  Twitter has even changed its blue to look more like Facebook's. Coincidence or a case of imitation being the best form of flattery?