In recent days two major exchanges Huobi and OKEX suspended deposits and withdrawalas of all ERC-20 coins. It is caused by bug called "BatchOverFlow" which is simple known for ages. It affected only one token(SmartMesh) which was using batchTransfer function. batchTransfer function is not included in the ERC-20 standard so if your contract code follows the standard it is safe.
Blockchain is cool technology but in that situation it is more like a hampering jail chain which stops everything and does not let to make any move. How is it possible that one simple error in only ONE not very known smart contract code pushed two exchanges to suspend trading.
Is blockchain great?
Yes it is if it is used with caution. Think for the moment if in the future 10% of the economy and business processes will be happening on the blockchain we will not be able to aford such a mistake. One bug may cause whole world to stop. And everyone knows there is no bug free software. Programming is the imperfect art, bugs in the blockchain are very expensive and there is no simple way how to handle with them.