Background: Non-fungible token (NFT) trade has grown drastically over recent years. While scholarship on the technical aspects and potential applications of NFTs has been steadily increasing, less attention has been directed to the human perception of or attitudes toward this new type of digital asset; in particular, about potential concerns that users may have around the use of NFTs.  Aim: The aim of this research is to investigate what concerns, if any, are expressed in relation to non-fungible tokens by those who engage with NFTs on social media platform Twitter, with special attention to possible concerns about crime, using NFT marketplaces, and market dynamics.  Methods: This research offers a mixed methods, largely qualitative, study. The method of data gathering is online non-participant observation of NFT-related posts and conversations on the social media platform Twitter. The methods of data analysis are topic modelling and thematic analysis, with additional attention to visual analysis of images and animated or video material associated with posts. Two datasets (with 18,373 and 36,354 individual tweet records respectively) were obtained for quantitative analysis; two smaller-scale datasets (both ca. 1000 records, with supplementary conversation details and visual material) were obtained for qualitative analysis.  Conclusion: This study proposes an interpretation of NFTs as functioning as ‘happy objects’ in NFT conversations on Twitter, wherein NFTs are represented as digital objects that hold a ‘promise’ of the happiness or fulfilment associated with financial gain. Concerns around NFTs as expressed on Twitter fall into broadly three categories: (1) concerns relating to not being to able to engage in, or being locked out of the possibility of, NFT trade; (2) concerns about the conditions, security and safety of engaging in NFT trade; and (3) concerns about whether any of the anticipated (financial) rewards or gains from engaging in NFTs will actually be obtained. Hence, many of the concerns that come up within NFT conversations on Twitter relate to conditions that may stand in the way of these happy object in fact bringing about their desired result. Overall, this study offers a better understanding of the expressions of attitudes of concern, uncertainty and possible experience of barriers associated with NFT trading. These findings contribute to theoretical insight, and can moreover function as a basis for developing practical (design or policy) interventions.