you said :the developers of a coin asking some fund to the community and investor to fund their project by ICO. but i was wondering if its not a kind of scam? what about if this developer give up on his project?
Of course! I am not saying that every ICO or crowdsale out there is a scam or is going to fail, but there are too many and there is always a risk of losing money in this kind of investment. It's up to you to take that risk. I personally have lost money in at least 2 cases (developers just took the money and disappeared). Read & learn, ask & search before participating / investing your money.
for your information, these are some ico case studies:
TheDAO raised 12.07M ETH
Ethereum raised 31,531 BTC
Waves raised 29,635 BTC
Augur raised 22,036 BTC
Lisk raised 15,128 BTC