I know that many good ICO's around and some were very promising. HOwever, there are other ICO projects to which now looks like an April Fools who's team always talk to much but in the end of the ICO period all they have to do is to be silent, list the coin of the project and then dump the project. This is why we really monitoring from these guys to keep their promises before, during and after the ICO period.
Such act is already beyond April fool, but a poor scam. There are different levels of scam and investors need to be very careful.
It might not occur and manifest during the token sales, they might list and just sell all they are left with.