I had an initial phone interview through a referral. The recruiter said he would be getting back to me within a few days. He also encouraged me to e-mail him if I hadn't heard anything. Normally I don't follow up with recruiters after a single phone interview, but because the recruiter suggested I do so, I followed through. The recruiter never responded to my e-mail and it has been over a month since I interviewed. In all fairness, the recruiter was very professional and easy to talk to, and I know recruiters have a tough job and it's hard to keep track of every e-mail. That said, if someone is interviewing through an internal referral and you ask them to e-mail you, it seems like good business practice to respond to the candidate's e-mail.