In comparison to centralised databases, blockchain technology offers better features such as privacy. However, a keen technology enthusiast will notice that the claim of complete privacy is not completely true because cryptocurrencies are not fully fungible. Fungibility means that one unit can be exchanged for another unit without any issues. An example is how a dollar can be exchanged for another one without any issues. Since the transaction history of blockchains is immutably stored, one coin or token’s history can be traced. This means that coins from legitimate sources are more valuable than those from questionable individuals. Main blockchains such as Bitcoin, Litecoin all suffer from this problem. For seamless commerce and value exchange between people this is a challenge that needs to be addressed. Herein lies one of the biggest problems.
The second issue is that many of the cryptocurrencies that try to solve this fungibility problem create the problem of possible collusion between different masternode operators. This is a risk that could leave a blockchain vulnerable especially to 51 percent attacks when only a few people or organisations control masternodes. This trust issue needs to be resolved to truly create a trustless system where there is both fungibility, privacy and trust in the validation process.