Correct me if I'm wrong, but I think it is fairly easy to detect the noise generated by this kind of tools and retrieve the real history, for example: users can generate a bunch of fake entries in their browsing history but if at the same hour every day they visit the same websites, well, that is some regularity that can be exploited.
Anyway, history can be sold even with noise, in this case users will see mostly ads about products in which they are not interested in, which could be, I think, much more annoying.
