SmartCoins in the BitShares ecosystem, Bit20 for example,  always have 100% or more of their value backed by the BitShares core currency, BTS, to which they can be converted at any time at an exchange rate set by a trustworthy price feed. In all but the most extreme market conditions, SmartCoins are guaranteed to be worth at least their face value (and perhaps more, in some circumstances). Like any other cryptocurrency, SmartCoins are fungible, divisible, and free from any restrictions.

You'll find the whole explanation in this page of the website BitShares.org that explain how the BitUSD and other smartcoin collateral works. In the case of BitUSD the value is pegged to the dollar, in the case of Bit20 the value is directly created by the witnesses. The collateral system that guarantees your asset is exactly the same.

Have a look, you 'll find it completely reassuring: https://bitshares.org/technology/price-stable-cryptocurrencies/