Martijn van Welie has a good perspective on emotional design: the behavior of an application causes us to project a personality onto it. Some examples from his post:

• Applications that throw windows promptly in my face are rough where as windows that fade onto the screen are far more graceful.
• An application that keeps on telling me about things I don’t understand such as error codes, format errors, compatibility issues is obviously more busy with itself rather than assisting me. A bit selfish perhaps?
• An application that keeps on telling me irrelevant stuff that don’t seem to impede normal usage is nagging.

He equates this with “brand personality.” I think we need to careful about changing application behavior to match brand personality — we need not match rough, whimsical or risk-taking with corresponding behavior, but I do agree that we need to be conscious about supporting the brand where we can and craft the experience of interacting with the application.

The article ends with a nice collection of guidelines for presentation, interaction, functionality and content. These are presented more on the good vs. bad spectrum than with the more human notion that many different types of personalities can be the basis of a supportive and trusting relationship. Nonetheless, its a good read.