Yup, social interface design rules not usability (although usability is still important). This is something Jon Husband of Qumana has been saying for several months now and he is right!

From Joel on Software - It's Not Just Usability:


Over the next decade, I expect that software companies will hire people trained as anthropologists and ethnographers to work on social interface design. Instead of building usability labs, they'll go out into the field and write ethnographies. And hopefully, we'll figure out the new principles of social interface design. It's going to be fascinating... as fun as user interface design was in the 1980s... so stay tuned.