I think that the biggest dumpers are teams of ICOs. They raise money from token sale, but that is not enough, they want to sell their tokens (30-50% from all existing tokens). WHile bounty hunters have only 2-3% from the total supply. So how can they cause a dump?
Yes, you are right. The main reason for the price drop is from their team. They even extend the time token sales with a bonus of 50%. I wonder. Why are they so enthusiastic to sell out their tokens at such a big discount. In fact, after that, they can not be listed on big exchanges.
Fair enoght. Team's working almost 24/7 and when ICO is over everyone (or not) wants to split his/her part. Bad or good, but we can understand them. However they usually take BTC and fiat but hold tokens. At least as far as I'm aware. They lock the tokens.