Some Samsung devices will display how many times the device has been flashed with unofficial roms.
There's an app on the market that removes it from some (triangle away) and there are USB jigs that will reset the counter. Not sure about the S3, but they work on the S2 and others. I have one from my S2.
XDA just posted news of a leaked jb for the sprint S3. Not sure how thar affects the one for c south.
Wouldn't stress the counter. It will rat you out if you have warranty issues but its usually just a matter of time before a jig is released to reset it. They're cheap. Think I paid $2 for mine.