I had a directory of video files that were all in directories:
Show/Season01/s01e*.avi
Show/Season02/s02e*.avi
And so on.

From the Show directory, I ran:
find . -iname *.avi -exec mv {} ./ \;

Which moved them all to the Show directory. I then removed the empty directories. For some reason, every single .avi file is now 4KB.
WTF did I do wrong? I know that I've done similar acts plenty of times without issues.