Where ever there is finance then there are also likelihood for scam to get associated to it as well. One thing we must know is that as the we keep advancing in the cryptocurrency space that is how people are discovering new ways of marketing and promotion, especially things are changing very faster in the space. And you are right, many project that ended up using any of those above methods to carry out their sales at last it usually ends that either the team made away with peoples funds, while some of the project ends up dumping after they finally got listed and investor won't mind offloading their bags and look for another more trusted and reliable project invest on.