I have a 2011 4 door that I bought new in Jan of 2011. Today I drove 3 co-workers to lunch. I'm 175 lbs. The front seat passenger weighs about 200 lbs, I'm guessing. 6'2", slight beer gut. One of guys in the back seat is 275 lbs, and the other guy is 325 lbs.
We drove about a mile away. On the way there I could feel the rear suspension hitting the bumpstops. The only thing I have in my trunk is about 15 lbs of tools. Once we got to our destination, no more than a mile away, three warning lights came on: the traction control off light, the hill assist off warning light, and a 3rd light to the left of the hill assist warning light. I can't remember what the 3rd light was.
I let the guys out as soon as I could. I then drove around the store (Cracker Barrel, I hate that place, not sure why I went) and parked. I took the key out and reinserted it and the dash was fine, no warning lights at all.
I did a half-ass search on here for passenger weight and load capacity, but I didn't find anything. I did find this via google:
Load Capacity, Personal Experience Only Please. - Subaru Impreza WRX STI Forums: IWSTI.com
They're talking about hauling 700 lbs worth of equipment, and one guy said he hauled that weight in mulch. I had 600 lbs of sweaty man ass in my back seat and I was bottoming out. That part didn't concern me too much, but the fact that all of those warning lights came on did concern me.
Ok so, I just checked the manual, (which I should have done before I wrote all of that) and the car has a 900 lb load capacity for passengers and cargo. I calculate that the 4 of us and my tool bag made for a total of about 1000 lbs. So, 100 lbs over the rated weight capacity will potentially cause the car to bottom out and will cause enough strain to bring up a bunch of warning lights on the dash.
I say potentially because on the way back we put the 325 lb guy in the front passenger seat and the ride back to the office wasn't too bad. I wasn't bottoming out and no lights popped up. The car felt fine on the way home too.
I guess this is my ultimate point: The manual says the combined passenger and cargo capacity is 900 lbs. It really is 900 lbs. That, and I have some fat ass co-workers.