I D which means Initial Coin Distribution is just a form of bounty that reward you after you must have done some task. Fresco did not give out tokens for free, they asked us to do some online test which you would be paid in fres if only you pass.
In Fresco's case the question really boils down to: Is it more scam free to do an online test and get tokens, or is it safer to just send some ETH/BTC to earn those coins.
It probably depends on how much you value your time or the information you give away for online test? Perhaps in some cases its cheaper to just give some dust amount of ETH/BTC after all.