I simply posted on my wall asking anyone who saw the post to like it. Of my 913 friends, 93 responded by clicking the like button.
If you do try, I would be very interested to see your results, but my thinking is that around 10% is an accurate assessment.
I have written before about the importance of being in control of your fan base and a strike rate of 10% could be considered pretty good for Facebook.
However, that is the amount of people that potentially see the post. It does not represent the people that are going to click through a link or watch a video.
This number is probably significantly less than the 10%.
In fact, based on the reaction I have had to things I have posted, I would say that it is more like 1%, and that's if the post is particularly popular.