I've seen two sources of memory leaks in Erlang based systems: 1) unbounded process message queues, and 2) passing binaries across process (pid) boundaries.

Many beginning erlangers run into these, and they're relatively easy to identify and correct. With a little practice, these become easy patterns to recognize and avoid.

As far as httpc, I'm unaware of that bug -- but I can say that I recently worked on a commercial product that leveraged httpc as a core component of the service, and it worked fine.