A person or entity that is famous for, in, on, widely known, publicized or celebrated in the cyberspace, internet or world wide web!
Some famous Cyweberties would include top internet providers like Perez Hilton, Heather "Dooce" Armstrong, Seth Godin, Michael Arrington, Matt Drudge, John C. Dvorak, etc... A Cyweberty of all time notoriety would have to include the likes of Bill Gates, Steve Jobs, Eric Schmidt, Larry Page, and Sergey Brin, (Executives, Google) and on...
A person that employs any means of high-impact marketing tactics informally known as "sign spinning". Sign spinners twirl, toss, and perform acrobatic style feats all while still ensuring the board's message displays prominently!
The person that stands in front of businesses and on street corners that hold up signs and toss them around, points, wiggles, wears or otherwise performs with them. Some are artists with hours of practice and many tricks and are very performing. They can be called a "Spinzist"!