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When a view displays an exposed filter or some other sort of form (e.g. Webform node) it becomes problematic if you use the time-based views caching for its output. You get forms pre-filled with other users' search terms/data and "illegal choice has been detected" whenever they are submitted.
It'd be cool if Views could somehow be smart about this and disable the renderable output caching option in the event that
<form> appears in its output somewhere.