Upon closer inspection today I noticed my Seidio case has scratch my phone as well. Not in the same place as the OP's scratch locations though. I have a small but noticeable scuff mark below the headset jack. Corresponding wear is at the same location inside the case itself.
You buy a case with a reasonable expectation that it will protect your phone from scratches, not cause them.
Like others, it is my belief that a simple solution is to provide felt lining above the camera cutout and below the kickstand cutout. This will eliminate flex and wiggle thus eliminate the chance of the case scratching the phone.
I've waited for Seidio to reply to my email and provide a solution, it has been 7 days of waiting so I decided to fix it myself.
I took an old polishing cloth that came with my iPod Touch. It's actually quite similar in thickness and touch to the "felt type" material used by Seidio. Also the width of the material was perfect. I cut two thin strips approximately 3/8 inch in size and used double sided tape to stick them down, (glue would probably be a better solution.)
The result is what this case should have been, snug, perfect fit. What's more, zero flexing, zero creaking.
If I have extra time I'll provide pics.