In the 128th episode of Semantic Mastery's weekly Hump Day Hangouts, a participant asked whether one should vary the URL when building links.
The exact question was:
When building links, is it better to use 1 and only 1 variation for example www. or http:// or just abc.com. I have heard varying advice where you would use all and someone else saying use 1 everytime you build a link.