If you search for Pump and Dump groups on the forum, you will see many. What they do is everyone invests at the same time which automatically increases the demand for that coin which in turn, increases the value. If a normal trader sees this increase then he too will join the tide and as soon as it reaches the top point the group takes out their money. Everyone else who joined will be in a huge mess.
Added to that pumps and dumps are only beneficial to the admin who buys coins before announcing the pump and hence get the most profit out of it. Others just fall for the trap. Pumps and dumps are mere scam but since the crypto market is unregulated and decentralised, therefore such groups aren't going anywhere. I would suggest you to stay away from them.
