On textured hull surfaces on racing sailboats: I think they were banned at some levels of competition because they were such a fantastically good way of pissing away money on a miniscule performace gain. And this is from a population that is not know for its frugality. The other downside was that many texture solutions involved adhearing thin textured films to the hull surface; the possibility of a piece coming loose and flapping in the water presented a much greater performance loss that any possible drag reduction.