Never have quite understood the term 'pump & dump' - however, if someone is excited about a stock one day thinking long term, and they suddenly obtain a big gain the next day, they may sell some stock. The biggest reason to sell is the 'shotgun' approach by short sellers that short everything! So, don't blame the pumpers, blame the dumpers....the shorts! The good story can remain the same, just that traders and MMs exploit the stocks....imo. If you love the story, hold on and avg in, or just don't buy bio if you cannot handle the heat.