If you lose Mid Lane it's ok because you can't be denied CS. AP Mids have farm abilities and they also can roam and get kills. See: Katarina.
Bottom Lane has a support to keep you in there CSing and plus you're so warded off you don't really have to worry about ganks.
Top Lane is constantly ganked, constantly harassed, and if you get behind the person ahead can freeze it and zone you. Or they can push it to turret and roam and apply pressure. This is why winning top is so important.
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Realo won gold at the Sex Olympics with a BROKEN FRIGGIN NECK.-Voltch