Here is something I think is more relevant when it comes to advertising your link on a blog.
That is not, like everyone thinks, is visitors!
Seems like everyone wants to know how many visitors a blog gets, how many are unique visitors, how many come from google, etc.
But no one ever asks:
How many page views does your blog get?
So a blog that gets over 12k visitors per month....
Gets 54k page views.
How many times is your link going to be shown?
Thus, do you want to buy advertising on a blog based on visitors?
Or based on page views?