Earlier quoted context omitted.
I think that this advice only applies to commercial sites. I have several personal domains such as Richard.sDoma.in and Richard.sMyNa.me which are far superior to any .com domain name. Personal users are only just starting to get into having a personal URL to hosting their own id and blog etc. and with over 2 billion internet users and only around 140million registered domains, I think attitudes will change quickly.…
Despite it being shorter, it seems more awkward to type and sometimes seems more prone to error. Not to mention how it might affect your standing with search engines. Remember when http://delicious.com was http://del.icio.us When I first saw the product, I thought the name was "icio".
This is why people just go to Google and type in the domain they want. If you're off by a character or two you still get to the site without a 404.