Fluctuations are to be expected Tomaso. The Steem team has even though about a way to counteract inflation and they added interest on the money kept in the Steemit Wallets. See the white paper or posts that detail this subject.
Nobody is saying it's not risky. We're talking about crypto here and volatility is at home, but the actions the Steem team has been taking so far have kept things under control (security implementations, accounts signup pause etc.).
Like I said, it's everyone's choice to take the risk or not. I always say don't ever invest more than you can afford to loose.