Okay, I just posted a picture below for you to see. This was my hair back in January. As you can see, the right side of my hair was significantly thinner. This is the result of 10+ years of wrapping. I was wrapping my hair, clockwise/to the right, since first pressing my hair senior year of high school. I never knew any other way to sleep with my hair, and I thought this was the best thing for it.
Wrapping, per say, is not a "bad" thing. However, if you are a nightly wrapper (like I was) then you need to alternate wrapping on both sides. One night, wrap to the left, the other night, wrap to the right. This way one side isnt getting overly stressed/thin.
In the last year (and since joining this board) i have stopped wrapping my hair. I am just no longer interested in wrapping it, because I dont like how straight/flat it makes my hair look. I find that it looks better in the morning when I sleep with a loose bun (and satin scarf or bonnet) or pin curl it. I think this is just because my hair has gotten longer, and I prefer that it have more body. And wrapping it, even after a nice roller set, takes away most of that volume/body.
Oh, and fyi, that right side has since regained most of its thickness/fullness, and i believe that is a result of overall health care (ie, moisturizing, healthy diet, protecting ends, avoiding direct heat) as well as mtg, which helped to thicken the hair shaft overall.
HTH.