Why copying with sudo cp is dangerous?

Question

linux

Hello!
What is the danger of copying *.iso file to a flash drive with the command line (sudo cp windows_7_x64).iso /dev/sdb?
Recently I tried this on a flash drive before copying there were all files and folders, everything disappeared after the command.
Thank you!

Answer 1

It is not customary to copy to /dev/sdb. Copy to /mnt/*.