Driver-side bed flex/bounce

[Hans Gruber]

So shortly after I got my truck I noticed that the driver-side of the bed will bounce or flex when going over bumps. But the passenger side doesn't bounce or flex at all (looks in review mirror as a jiggle of bed). I've never been worried about this but I was curious: Anybody else notice this?

I googled the issue once and found a few posts for various trucks, usually on the driver's side. Just a function of driver weight affecting suspension give-and-take or something I should worry about?