I don't think it's about stretch marks it's about anything being real on these women!
Trust me, as a decent level photochopper myself you can see what they've done 90% of the time.
IMO at least, blemish removal and a slight airbrush are fine, however they don't stop there - at all.
Teeth are brightened/changed, body shape is warped, it's just too far!
The funniest thing I've ever seen in my life was on a magazine like heat.
EDIT - I can't believe it, but I've found the image....
Someone tell me what the mistake is on this picture... WHICH IS ON THE FRONT OF HEAT.