The modern mis-spelling of definitely seen in almost every modern example where a spell checker was not deployed, most commonly in internet chat, probably from its mis-pronunciation by modern youth and/or being confused with unfortunately.
The most common spelling of the word "definitely" in internet forums, comment pages, and chat rooms. If you pay attention, you will find that "definitely" is actually the second or third most common spelling. Alternatives include "definatly", "definetly", or best of all "defiantly".
Microsoft's Zune is Definately no iPod - and the person who made that digg post is definitely no English major.