If your nose happens to get plugged from allergies, this could be dangerous. You would probably wake up before suffocating but I'm not a doctor so I dunno.
I have heard that some CPAP machines have a foam that degrades and makes it's way into people's lungs which is scary. And they aren't even necessarily cheap CPAP machines. Just, buyer beware on that front too.
I think everyone should just be making whatever decision is right for them and their circumstances.