Potential barriers that may impede the fast adoption of Non-fungible tokens (NFTs) in the identity space.

1. Lack of standardization: Currently, there is no universally accepted standard for creating, managing and using NFTs. This makes it challenging for developers and businesses to create interoperable NFT-based identity solutions that can work together seamlessly.

2. Scalability: As NFT adoption increases, there is a concern about the scalability of the underlying blockchain technology. Due to the complexity of creating and managing NFTs, scalability becomes a significant issue, and this could slow adoption.

3. Complexity: Building and deploying NFT-based identity solutions require specialized knowledge and skills in blockchain development, making it challenging for developers to create mainstream user-friendly applications.

4. Regulatory issues: NFTs are still a relatively new technology, and regulatory bodies have not yet established clear guidelines on how to incorporate them into existing regulatory frameworks.

5. Security: As with any technology that deals with sensitive information, the security and privacy of NFT-based identity solutions are crucial. However, cybersecurity threats are on the rise, and this presents a significant challenge to widespread adoption.