Twitter shows us that size matters, but shorter is better!
Its long time that many websites do not use .html like suffix. Remember spammer use longest urls with most important keywords. And many popular websites ie: Digg, Drupal, Twitter do not use www. in hostname(just Dmoz changed to www. in the last time). Web is getting mobile, also not everyone using internet with a full-keyboard, many users are getting information with cell-phones or similar small devices without a full-keyboard. Therefore it is getting more important to have short urls.
Also just hostname and id(numbers) will be the next genaration url: example.com/123456. Why numbers and not letters? Letter-system could be shorter (Tinyurl like services are already using letters), but... Imagine you have to give an url on the phone to someone who does not speak your language perfectly. Letters would confuse(accent, prononciation, case or not, which alphabet). Remember russian and greek languages have similar letters like P,R for other vocals. But numbers are magical. Everyone can spell and understand numbers from one to ten in english. And old golden-rules(meta-tags, domain, url, ...) plays no role anymore for major search engines. Also start to cut!