Vehicles today contain a multitude of sensors creating vast amounts of data. For many applications, these data need to be shared with other entities so that they can also utilize it. Vehicle-to-everything (V2X) is the amalgamation of all potential vehicle communication systems. V2X technologies are enabling many smart-vehicle applications, such as autonomous vehicles. However, in utilizing these data from external entities, vehicles rely on the availability and trustworthiness of centralized entities who may be able to delete, forge, leak, or otherwise tamper with the underlying data. Blockchain technology provides a decentralized mechanism to allow vehicles to validate data they receive in a trustless manner. This paper explores potential applications of blockchain technology in the V2X space, categorizing and analyzing use cases based on their underlying blockchain requirements. It then uses this analysis to determine the key requirements behind an effective V2X blockchain.