Right, and what I was trying to say (which maybe didn't come through) is that if you're not super pilot and don't do a perfect 1G roll, you will start getting relative wind angles, interference drag and potential stability effects that the aerodynamics people weren't necessarily obligated to look at. It's more about the potential for surprise of something unexpected happening half way through the maneuver - and how the pilot reacts to that surprise - rather than any concrete structural or aerodynamic limit.
I'm not advocating breaking FARs and doing aerobatics in a non-aerobatic airplane either, just saying that test pilots do envelope expanding maneuvers all the time, and the trick is to not do dumb stuff when unexpected things happen.
Edit: I can see this thread has devolved into people talking about all kinds of random stuff... Sustained inverted flight... Fluids pooling in different parts of tanks, etc. To be clear, we started talking about a QUICK +1G aileron roll with no sustained inverted flight. When flown correctly your butt stays on the seat the whole time, Bob Hoover can pour his tea, etc. In that case the relative wind is the same as it always was and there's no reason to worry about fuel or oil pooling in weird places it shouldn't. But then you've probably flown with someone who's like "hey watch this!" and rolls the airplane and you get that lurching feeling in your stomach upsidedown and your butt comes off the seat. At that point you're at less than +1G. It's a subtle argument but since people make mistakes and don't always fly maneuvers perfectly, that's when I would start to worry about something weird happening.