In a recent article at A List Apart,  Patrick Lynch summarized (and enhanced) Don Norman’s hypothesis from his famous book ‘Emotional Design’. To quote:

Why attractive things work better
In psychology, emotional reactions to stimuli are called affective responses. Affective responses happen very fast, and are governed in an automatic, unconscious way by the lower centers of the brain that also govern basic instincts (food, fear, sex, breathing, blinking, etc.). Think of affective responses as the brain’s bottom-up reaction to what you see and feel. Cognitive responses are your brain’s slower, top-down, more considered responses. They’re governed by your personal cultural views, learning, experiences, and personal preferences that you are aware of and can easily articulate. Affective reactions assign value to your experiences; cognitive reactions assign meaning to what you see and use.
Affective and cognitive responses to visual stimuli are governed by a three-stage process in the brain, at visceral, behavioral, and reflective processing levels:

In his talk from 2003, Norman turns his incisive eye toward beauty, fun, pleasure and emotion, as he looks at design that makes people happy. He names the three emotional cues that a well-designed product must hit to succeed.

Digital marketing agency released a comprehensive Social Media playbook, and you can download it free from Scribd.

360i Social Marketing Playbook

Some quotable bytes:

If today consumers can easily avoid commercial messages they deem intrusive,  annoying, or irrelevant, then the central way to  engage them is to engage with them. Listen to them.  Respond to them. Take their ideas seriously. Change in response to their interests

Social media are highly effective in the middle of the purchase funnel, to improve brand or product consideration during the period when consumers are gathering opinions and listening to word of mouth