One of the potential issues in the adoption of smart cities is the non-interoperability of the divergent technologies. As of now, you can find many technologies working independently in urban environments. This will be a challenge to handle, and only IoT's vision can become the base here. It has the capability of unifying information and communication platforms, which makes it a strong candidate for smart cities. As of 2017, a strong technical model for a unified Internet of Things is still lacking, but as the technology is evolving, we can expect it to converge into one big IoT bubble. 

Another important technical challenge is to make IoT simple for the masses. The adoption rate for IoT technology is not as fast as it can be. The vision of it being a trillion-dollar industry will not be realizable until it is easy to use. It will be a challenge to convince developing countries to adopt the concept of smart cities.