It depends on the project. The company I work for is a small web company, and we work mostly through marketing agencies. Most of the time, we talk with the agency we're working with and they act as the middle man between us and the client. On some projects, though, we do collaborate directly with the client that we're building the site for. Mostly, though, we're talking with "internal" clients, usually project managers and designers at the marketing agencies we work with.