As I observed yes some of the tokens price on exchanges may fall below the ICO price because some of the tokens token holder (bounty participants) sell their tokens after they received their token. Yet they will recover as time goes .Off course, the project itself has to be very good to sustain the value.
Bounty participants as well the investors who get high bonus sometimes sells it right after ICO to earn more profit by themselves. That makes the project slow in progress.
Most of the bounty programs do not account for more than a couple percent. That can never be the reason why the price tanks. If the project is good, or the sentiment in the market is good, the price ofter doesn't tank!