I took a quick look around and found this, for discussion mainly, and because it relates to knee wraps, it makes sense to place it in this thread as well:
In chapter 4 of the NSCA textbook on biomechanics, here is what it says about knee wraps.
"It is not unusual for individuals to use knee wraps during training or competition. The wraps vary from thin, elastic, pull-on variety [to me this means sleeves] that can be purchased in drug stores to the heavy, specialized wraps sold only through weightlifting supply stores. . . Very little research has been done on the efficacy of knee wraps. Detrimental side effects have been reported, however, including skin damage and chondromalacia patellae, the wearing down and toughening of the posterior surface of the patella.
Though there is no available evidence that wraps protect the knee against injury, an experiment conducted by Harman and Frykman showed that wraps can improve performance. Through a spring effect alone, heavy wraps around the knees added an average of 25 pound to squat lifting force. The notion that warps work only by stabilizing the knee, lessening the athlete's fear of injury, or providing a kinesthetic cue is incorrect. The wraps actually provide direct help in extending the knee. On the basis of lack of evidence that knee wraps prevent injury and the opinion of a number of health practitioners who assert that knee wraps can actually cause injury, athletes should probably minimize the use of wraps. If used at all, knee wraps should be limited to the sets with the heaviest loads" (86-87).
There's a bit more of a discussion there on it if anyone wants to read it further, but I think the general consensus is that they're not an issue.
I've yet to read of anyone that has had issues caused by knee wraps, as in I haven't read of anyone here or on other forums mention such problems which makes me wonder where the health practitioners come across their info....though that may be because they see more people, in general anyway, so they're bound to come across someone that has had an injury to the knee but that doesn't necessarily equate to it being the result of the knee wrap either; sometimes, doctors assume the cause, IMO. It could easily be the case that people that have had the knee issues were prone to them anyway and skin damage may be related to high reps as Evilinmotion suggests, possibly due to the time they've had the wraps on or even by those that omit to remove them and let the blood circulate, especially if new to lifting and not being aware of the need to remove them periodically etc.
Just a thought.