[I]f you make it easy to talk to me, I will immediately be a lot more likely to keep talking.
Zeus Jones has a great write up about using conversational language and cues to invite users through interactions. The deconstruction of the lazy trial/registration process in Tumblr is used to demonstrate how this type of engagement makes the learning process natural and inviting. The discussion picks up on the Cluetrain meme of markets as conversations, positing that systems are conversations, and turning front ends into actors that use conversational language as interface. Afterall, if software is to be social, then it may as well learn social skills.
http://www.zeusjones.com/blog/2009/conversational-ux-design/