Balderick said:
Most bikes will weigh more than their front wheels, and the greater mass assists in ensuring the wheel is properly seated on the axle. If it is not properly seated the theory, as I have been told, is the weight is supported by the QR, not on the axle (where it should). Just because you have not had issues in the past does not mean you will not in the future - ongoing added strain on the QR may lead to that QR failing in the future.
No I will not have problems in future, because prior to riding, I check the bike over. A tell-tale sign of the wheel not properly mounted is as grouch mentioned, the wheel will appear not to be true between the forks. My point is that even with mounting the wheels right side up, you could mount them crooked as well.
Loosen your quick release, lean the bike slightly to one side, and tighten the QR again. Thats going to give you an improperly mounted front wheel.
That has been my experience, and in the cases where I have had to mount the front wheel upright, I lifted up the front of the bike at the hub, to ensure that its sqaurely fitted into the dropouts before tightening and closing the QR lever.