Facebook just launched and updated header and it's raises an issue we designers should be aware of. If your users habitually use your product, like many Facebook users do they develop muscle memory for the tasks they complete most often. Before you decide to move an access point to a feature or play with the flow give some really good thought to how this will effect your most faithful users.
This is the old header:
Notifications and access to friends, messages and activity are on the left.
Here is the new one:
They've moved the notifications and access points to the right! Very annoying for a user that has been using the site for a long time. I see lots of wasted mousing and tapping motions going on over the next while.
I wonder why they thought this was an important redesign?
One other point. Re: this new gigantic search box - isn't it form design 101 to make the size of the text box relate to the number of characters the user might enter? Maybe that's old school but one of my pet peeves.