I disagree. I know plenty of guys who aren't huge, don't use AS and have stretch marks. I have some myself, though not as bad as some peoples. It really depends on the person. Making sure you stay well hydrated and using things like cocoa-butter and moisturizer on problem areas(Generally, guys get them near the pec insertion points and shoulders.) will help prevent them. But if you put on a fair amount of size quickly you may get them anyway.