Think of an ICO as a startup, and buyers of the tokens are early-stage investors.
Early stage investing is the riskiest type of investment out there. People who invest in such projects typically spend a long time researching the company, the people, and even getting to personally know and interview the founders.
There is currently so much hype about cryptocurrency that people throw lots of money at ICOs that they don't know much about. Do your own research, make sure you really know what you're buying. Otherwise, you'll lose money and have no one to blame but yourself.

I spend a lot of time researching before investing in ICOs. I always have a list of promising projects that I'm looking into and study in depth before buying.

My top 3 right now are:

www.waxtoken.com
Online virtual asset exchange secured by blockchain technology

www.filecoin.io
Cryptocurrency incentivized and secured, distributed cloud storage

www.MindSports.IO
Online games such as Chess, Poker, Shogi, Go, etc. Playing, spectating, and betting. All transactions secured on a blockchain.