Has anybody had this done? I bought it from Groupon because it was half price but now I'm really having second thoughts. It says it's fine to use on colored hair but my hair is really thin and straw-like from years of blonde highlights. Plus I'm scared of all the chemicals that could potentially be in there - especially the formaldehyde. They say on the Groupon that there is no formaldehyde in the keratin straightening treatment but how can you trust that? Also not sure if it's worth the money for something that could either make my hair fall out or last only 3-4 months. Anyway, if anybody has any experiences with this I'd appreciate your perspective.