Last year alone we did close to 20 or so roof cleanings for the very same reason. Insurance company's were going to drop them because their roofs looked nasty to the point of looking like they needed to be replaced. Once we were done cleaning the roofs they looked brand new. Not sure what the outcome was with the insurance company's but I would bet that they went ahead and renewed their policy. As far as HOA's, a very large part of our work comes from clients who receive letters telling them to clean their roofs, houses, and concrete. One of the jobs we are doing tomorrow is for just that and we have 3 tile roofs we are cleaning on Friday in a community for residents who receives letters.