There has been a lot of ICOs where the price of the sold tokens have dropped so much and adoption has been so low they can be considered to be fails. And that's the ultimate risk of ICO investing, either your project turning out to be a scam or does not go as high as you think it will.

The failure rate imo is probably around 80%. Most ICOs don't even reach the top 200 tokens.

If anyone tries to sell you the idea that ICOs have zero failure rate, they must be high.