I agree with Liviu A, if you read and write from left to right, you (the user) will definitely focus on the content starting from left to right.
Knowing this, it's all about priority.
Have you ever wondered why when you watch TV the television logo is on the right (not on the left)? Because they consider it secondary. The main focus is on the broadcasted program and the logo is not actionable (you can't click on it) it's just informative.
On the web it's another story. The logo is actionable (part of the navigation), usually when you click it you go to the homepage.
So it's about prioritization/information architecture.