Low availability of blockchain skills
As with any new technology, the number of skilled personnel will be limited. In the case of blockchain, this natural order is made far worse because of the large and growing number of systems. Looking only at the major chains, systems are written in C, C++, Java, Scala, Golang, and Python. All of these systems have different architectures and protocols. The blockchains that have smart contracts have different contract models, contract APIs, and even completely different programming languages, such as Solidity and Serpent.
On the security front, each blockchain system has subtly different security models and challenges. The simpler the system, the easier those requirements are, but the less the blockchain will be able to do. Moreover, because of the recent surge of interest, blockchain skills are very expensive on the open market. In particular, top talent with a proven track record is very hard to find.
