If I remember it right, the idea was that in a roll over, you're going to scrape right along that gas cap and have an invitation to spark and ignite.
The actual chances of that happening are probably incredibly slim, but a lot of us relocate it just so it's out of sight, out of mind. If you have the money and it worries you, I'd say just change it for piece of mind. Otherwise, try not to flip any trucks!
