The limited quantity of email lists continues to present a problem to business-to-business marketers, according to BtoB Online (via MediaBuyerPlanner). Eric Snider, executive vice-presodemt at catalog direct marketer SkillPath, said, "There aren't too many email lists out there in the marketplace." Though there are plenty of list marketers who would like to play a role, email names for rent are "pretty limited," he said.

Part of the challenge is that marketers want to protect the identity of their customers, particularly when getting permission to send email can be so hard-won. Other challenges include spam and phishing, as a result of which, for a large majority of marketers, email is still a retention vehicle rather than one used for acquisition.