Because it's the first dissertation defense I've heard about that will be both live-streamed and live-tweeted on Twitter. Lee is the blogger behind Urban Science Adventures (read her last-minute thought on her defense here) and she Tweets as @FeteSociety. You can access the live stream at http://stickam.com/dnlee5 and follow her defense on Twitter using the hashtag #LeeDefense. (Lee herself won't be tweeting. She'll be rather busy.)
We at Science Careers wish soon-to-be-Dr.-Lee excellent luck.
(Speaking of Twitter, you can follow me @SciCareerEditor.)
Update: At approximately 1:30 p.m. eastern time, Danielle announed to the world, via Twitter, that she is now officially Dr. Lee.