On high-throughput, low-fee blockchains, a qualitatively new form of maximal extractable value (MEV) has emerged: searchers submit large volumes of speculative transactions, whose profitability is resolved only at execution time. We refer to this as spam MEV. On major rollups, it can at times consume more than half of block gas, even though only a small fraction of probes ultimately results in a trade. Despite growing awareness of this phenomenon, there is no principled framework for understanding how blockchain design parameters shape its prevalence and impact. We develop such a framework, modeling spam transactions competing for on-chain opportunities under a competitive equilibrium that drives their profits to zero, and deriving equilibrium spam volumes as a function of block capacity, minimum gas price, and the transaction fee mechanism. Empirical evidence from Base and Arbitrum supports the model: spam grew sharply as block capacity was scaled up and fell when minimum gas prices were introduced. Our analysis yields three main insights. First, spam is always costly: when block capacity is scarce, it displaces users and drives up gas prices; as block capacity grows, it increasingly consumes execution resources, raising network externality, i.e., the cost of provisioning and processing blocks. We show that spam takes an increasing share of each additional unit of block capacity, so capping it before all users are included creates a favorable trade-off: forgoing a small amount of user welfare eliminates disproportionate spam and externality. Second, we extend the analysis to priority fee ordering and show that ordering transactions by gas price helps reduce spam, as spammers must pay more to reach early block positions. Third, as user demand grows and blockspace is scaled accordingly, spam's share of block capacity plateaus rather than growing indefinitely.

翻译：在低费用、高吞吐量的区块链上，一种新型的最大可提取价值（MEV）已出现：搜索者提交大量投机性交易，其盈利性仅在执行时才能确定。我们将此称为垃圾MEV。在主要汇总链上，它有时会消耗超过一半的区块Gas，尽管最终只有小部分探测会产生交易。尽管对此现象的认识日益加深，但目前缺乏一个原则性框架来理解区块链设计参数如何影响其普遍性和影响。我们开发了这样一个框架，将垃圾交易建模为在竞争均衡下争夺链上机会（该均衡导致其利润为零），并推导出作为区块容量、最低Gas价格和交易费用机制函数的均衡垃圾交易量。来自Base和Arbitrum的实证证据支持该模型：随着区块容量扩大，垃圾交易量急剧增长；引入最低Gas价格后，垃圾交易量下降。我们的分析得出三个主要见解。首先，垃圾交易总是代价高昂：当区块容量稀缺时，它会挤占用户并推高Gas价格；随着区块容量增长，它越来越多地消耗执行资源，从而增加网络外部性，即供应和处理区块的成本。我们表明，垃圾交易占用了每一额外区块容量中越来越大的份额，因此在所有用户被包含之前对其进行限制，会产生有利的权衡：牺牲少量用户福利可消除不成比例的垃圾交易和外部性。其次，我们将分析扩展到优先费用排序，并表明按Gas价格排序交易有助于减少垃圾交易，因为垃圾发送者必须支付更高费用才能获得较早的区块位置。第三，随着用户需求增长和区块空间相应扩展，垃圾交易在区块容量中的份额趋于稳定，而非无限增长。