We study a model where some investors ("hedgers") are bad at information processing, while others ("speculators") have superior information-processing ability and trade purely to exploit it. The disclosure of financial information induces a trade externality: if speculators refrain from trading, hedgers do the same, depressing the asset price. Market transparency reinforces this mechanism, by making speculators' trades more visible to hedgers. As a consequence, issuers will oppose both the disclosure of fundamentals and trading transparency. Issuers may either under- or over-provide information compared to the socially efficient level if speculators have more bargaining power than hedgers, while they never under-provide it otherwise. When hedgers have low financial literacy, forbidding their access to the market may be socially efficient.