Every new technological revolution goes viral before we could have a taste of its failures but through modern research & developpement techniques, the community learned a lot about the issues and limitations of blockchain technology.
Complexity : it is easy to talk about blockchain just like in this article, glorify it and give a whole saint graal thing to it but in reality the disciplines behind this technology are far away from being democritized and it is definetly not easy to aprehend and the highly specialized industry is chock-full of jargon.
Network size : It requires a large number of nods knowing that each user is a nod that means that the bigger the network is the stronger it responds to attacks but the risk of internal defects remains. Size Matters !!
Moreover It does have a physical limit, since all the Data needs physical storage.
Transaction costs, network speed : Today’s representative blockchain such as Bitcoin takes 10 min or longer to confirm transactions, achieve 7 transactions/sec and and each transaction costs about $0.20. Clearly, a large gap exists between where Bitcoin is today, and the scalability of a mainstream payment processor. Taking too long to get it Done !!
Human error : If a blockchain is used as a database, the information going into the database needs to be of high quality. The data stored on a blockchain is not inherently trustworthy, so events need to be recorded accurately in the first place.
The phrase 'garbage in, garbage out' holds true in a blockchain system of record, just as with a centralized database.
Unavoidable security flaw : There is one notable security flaw in bitcoin and other blockchains: if more than half of the computers working as nodes to service the network tell a lie, the lie will become the truth. This is called a '51% attack' and was highlighted by Satoshi Nakamoto when he launched bitcoin.
For this reason, bitcoin mining pools are monitored closely by the community, ensuring no one unknowingly gains such network influence.
Politics : Because blockchain protocols offer an opportunity to digitize governance models, and because miners are essentially forming another type of incentivized governance model, there have been ample opportunities for public disagreements between different community sectors.
These disagreements are a notable feature of the blockchain industry and are expressed most clearly around the question or event of 'forking' a blockchain, a process that involves updating the blockchain protocol when a majority of a blockchain's users have agreed to it.
These debates can be very technical, and sometimes heated, but are informative for those interested in the mixture of democracy, consensus and new opportunities for governance experimentation that blockchain technology is opening up.