Yes, probably both investors and bounty participants at the same time! Many people believe that the bountists are stupid and sell everything at once, but this is a misconception. Many of them wait for months to sell.
Both of them have a responsibility about the dump,
And about bounty participants are waiting for months to sell it is not correct at all, most bounty hunters are looking for a quick gain. That was why the price got dumped instantly as soon as it gets listed on any exchange. We can not deny it, only a handful people did that. But the majority did not do that because they need money as soon as possible to pay their needs.
Ah thats right, its not about you are bounty hunters or ICO investors. But, its all about your personality how to manage your token/coin which you got from new altcoins.