Yup, LePaul nailed it. DA can be a killer. I got my PPL at the Academy, where the runway sits at 6,500 feet MSL. Throw in a nice summer day when the temperature is in the 70s or so, and suddenly the DA at the field is up around 9,000+. We flew Cessna 172s, and all but the newest ones had a DA limit of 9000. Anything higher than that, we were grounded (the SP models had a limit of 9,500, IIRC).
Actually ran into it first hand by accident though. I took off when the DA was still within limits in an older plane (circa 1972 I think), flew for a while, and was coming back to do some pattern work. Landed the first time, taxied back, and was going to take off again. I had no way of knowing that the DA had gone above limits while I was out flying. Ended up having to abort that takeoff because I wasn't getting 2300 RPMs out of the engine. I'm just glad that I landed that first one and didn't try to go around. Not sure the plane would have been able to do it.