Change "w" as a quick key between normal and preview mode!!!
This letter changes between normal and preview mode hiding bleed and pasteboard. It also if you mistakenly are in a text box removes entire editorial sections causing thousand in reprint costs. Everyone I know has had this disaster happen to them and all complain about this. Please change the default to a combination of keys to prevent these problems. We will have to get used to it but everyone will thank you.

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Mårten Kellerman commented
I agree that it is ill-advised to use regular keys (with no control/option/command pressed), since it's all too easy to find yourself editing some text and then be navigating to another page/spread and forget that you are still in a previously viewed text frame, and then keep entering ’w’ several times in a text frame that isn't even on screen anymore.
All keyboard commands should always be accompanied with a modifier key.
That said, anyone can easily create a new key command for preview mode, so I did just that (Under Tools > Toggle view setting between default and preview). As long as you remember to use your custom key command, the problem can be avoided.
(Adobe should still fix the problem though.)