No. They aren't gross at all. Even I have them on my ass. Stretch marks are something which you cannot have control over. No, and that is not a turn-off. To me, it is a turn-on as they represent a design pattern on your body, much like the vinyls that we have on our cars :-)
If the stretchmarks are minor then it really won't be noticed. Most guys will be too busy studying your overall sexyness. If a guy notices your stretch marks you have more to worry about in terms of why he's not looking at your other parts.
The horizontal tiny thin marks, I think everyone gets from time to time. What gets me are those thick vertical marks, mostly along the sides of the waist, which look like lightening bolts or old scarred stitch-jobs. Yikes! Although I can't say they are deal breakers as far as "bumping uglies" goes. As long as the person that has them doesn't want to go to the beach or on a cruise.
no, they are no problem at all. if I seen a girl had them, it would not turn me off at all. they can be quite cute actually. if it really does bother you even though it shouldn't, you should try rubbing coco butter cream on them, I heard that fades them a little when done frequently. DO NOT WORRY AT ALL. if a girl is hot, then that is the end of it, she is hot. if any boy has a problem with them then they are just nitpicking.
Most guys don't really even care. We examine ourselves and are overly critical. If you are already cute then the guy is most likely checking you out and not trying to examine every part of your body with a magnifying glass. Don't worry about it. Especially if you are tiny anyway. Everyone has a few.