Do hard shell cases scratch iPhone 5?

Do hard cases or snap on cases scratch the iPhone 5? Went phone case shopping today wanted a silicone case but they didn't have any (-.-) all I saw were hard cases and this seller at a shop warned me that hard cases aren't good for the iPhone 5 as it could scratch its side.

I have a hard case on my phone and have had one on a blackberry and it didn't scratch mine
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I have a monogrammed case for my iPhone 5 and it looks so cool. No any chance to scratch inside. You can also try it. It is available as many patterns and colors to choose.