With the exception of PR people everyone speaks for themselves. Before this post did you think Pogue spoke for mac enthusiasts everywhere?
Translation: "I do not agree with David Pogue"
The phrase "speak for" is an idiom and is not meant to be taken literally.
"speak for yourself: expressing a desire to dissociate oneself from what another has just said or the assumptions behind it."
How many people put "can" in front of the idiom?
There was a Simpsons reincarnation joke that used the phrase:
Sideshow Mel: You only live once! Apu: Hey, speak for yourself!
http://en.wikiquote.org/wiki/The_Simpsons/Season_9#Miracle_o...