I once hold a coin and suddenly the coin that is almost $1 dump to less than $0.01 to me I move on but to some people which are newbies this can discourage them from participating in crytocurrency and make them conclude it is fraud and that brought me to a question how do you think pump and dump group are damaging crypto-currency and it's reputation??
Not only BTC market is affected by "Pump and dump" (P&D), this practice is in every trading market. Take example of Equity Trading for instance, you can see huge market swing in both direction (up and down) on any single trading day. That manipulation is done by Big investors who are holding majority of the shares. Although BTC is decentralized and distributed ecosystem, still there are WHALES who have gathered majority of BTC over times and now are in a position to manipulate the BTC market. Rule of thumb is to keep your nerves strong and never ever pay attention to P&D and FUD, HODL is key to success in every market and holds true for crypto market as well.