The following are my defenses:

• a blockchain exists that can be explored and checked for veracity (www.steemd.com)
• each individual block can be inspected
• the project is open source
• a number of developers are building on it, enhancing my trust in the safety and security of the underlying code
• I have never heard of a 'zero day exploit' being built into a blockchain/distributed computing platform
• Given my understanding of bitcoin and the technology that makes it possible, my trust in Steem is enhanced primarily because it builds on the security of bitcoin indirectly