I think most of the shit coins occur as a result of too much hype in the project with little or no product usage. This normally lead to low demand of the coins and those who notice this on time will have no choice than to dump before it gets more lower. Some time project put up lots of attractive features with having them in their schedule just to draw the attention of potential investors who knows the value of product usage that's it always advisable to do lots of research before taking decision.