TechCrunch is taking on the 17-year-old Demo conference. Check out Brad Stone's article in the New York Times, "Amid Conference Halls and Keynote Speakers, a Rivalry Forms," which describes the situation. Michael Arrington, TechCrunch's founder, is using his blog and Twitter to promote his conference which coincides with Demo.
For PR folks, the thing to consider is this: Sept. 7-9 (Demo in San Diego) and Sept. 8-10 (TechCrunch50 in San Francisco) will be busy times for West Coast tech reporters. Advise your clients not to consider media tours that week.