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Incidentally, Single Sign On has something to offer here. If a user has only to authenticate once and then her entire web session is authenticated, and if resources she accesses can detect this authenticated state and jump directly to logged in state, then the need to play these non-logged-in guessing games is lessened. Logging in is a good thing. The authenticated experience should be so compelling, so effectively present exactly what the user didn't even realize she was eager to know, that users should be logging in.
See also
See also Authentication versus Customization.
On predicating guest content display upon requestor IP address
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