Warning doesn't work but investors losing money does makes them learn.
You can learn from both angles depending on your nature.
It is far better to yield to corrections and warnings, than wait to make the mistake yourself before learning. Sometimes, the mistake made might be grievous and sometimes irreversible.
That's inevitable. You will make your own mistakes and you can't just simply watch others make them and learn from afar. And a lot of people made mistakes in the past trusting icos that ended up as scams. But i think the more popular ones and the ones making big noises before launch will garner support. So yeah, icos will still survive i think.