It is interesting that they feel the need to officially deny it. The Twitter user co-hosts a podcast where users can call in to tell him whether they think Facebook is listening or not.

One could argue, from a PR perspective, it does not matter whether Facebook is listening or not.

First, some users do not trust them. Maybe Facebook is worried about those users telling other users.

Second, some users believe it is technically feasible to listen.

Finally, there is no legal/regulatory framework in the United States to effectively stop Facebook from listening[FN1], if they wanted to do so. They have clear business incentives to listen because the objective is to gather more personal data about users than their competitors.

NB: Added "in the United States" for clarification.

FN1. Incorrect? What are the theories of liability? What are the sources of law or regulation in the United States? Is injury required? What is the injury? How does one prove the injury?