In and of itself, the acts of Sherri and Tyra showing their real hair aren't a bad thing. However, it's the fact that these incidents are part of a larger pattern, and in Tyra's case, a much-hyped marketing blitz, that is troubling.
In Sherri's case, I truly believe she just doesn't know any better. She's a dullard with a good heart who likes a good laugh and to speak her mind (or what little of it exists). In Tyra's case, while she's certainly lacking in intellect and depth, there are ulterior motives behind her shenanigans. I know that she definitely has delusions of grandeur and is somewhat self-unaware, but there's a method to her madness.