Erin Malone @emalone
If you ever voraciously read the book Designing Social Interfaces or visited designingsocialinterfaces.com, then you've already been learning from Erin. And congratulations, because she's a pioneer of the kind of strategic, effective social design so many of us rely on to make decisions online.
In fact, while directing the Platform UX Design team at Yahoo!, Erin led the building of their Design Pattern Library. She also spearheaded the redesign of Yahoo's registration system and oversaw the redesign of the giant's Developer Network. In other words, the kinds of products you've probably used time and time again.