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Some people deal with confidential files and use Dropbox for these. It would be very useful to allow people the option to clear their "Recent" files at will to allow more privacy and discretion.
It's difficult to explain how angry I feel when I open my laptop at customer site and let all the neighbourhood know about my projects and other customer, as I tend to use descriptive file names ... I guess as almost everybody. I have started looking for some other solutions and also have stopped recommending dropbox.