How important are poster sessions in conferences? Many times I've attended and will attend international conferences presenting a poster in my life.
I used to think that this poster works have been considered less important than scientific papers or oral communications, but important anyway for scientific divulgation.

So, when presenting a poster, I've always been thinking: "Okay, it's not as important as a oral communication, but, if they accepted it, this means they found it interesting".

Then I read the "Ten Simple Rules for a Good Poster Presentation" article by Thomas C. Erren and Philip E. Bourne, and I was pretty disappointed after reading point 4:


  Rule 4: Poster Acceptance Means Nothing
  
  Do not take the acceptance of a poster as an endorsement of your work.
  Conferences  need attendees to be financially viable. Many attendees
  who are there on grants cannot justify attending a conference unless
  they present. There are a small number of speaking slots compared with
  attendees. How to solve the dilemma? Enter posters; this way everyone
  can present. In other words, your poster has not been endorsed, just
  accepted. To get endorsement from your peers, do good science and
  present it well on the poster.


Do you agree with this statement?

What is the overall importance of a poster session during an international conference?

Is is just a way to collect subscriptions and money, or is it an important occasion for science divulgation?

Thanks

Edit: I'm speaking about poster session vs. oral session, I do know that a poster with presence is better than nothing. As Woody Allen once said: "The 80% of success is just showing up" ;-)
A poster session is a good way to disseminate your work: but it has nothing to do with how you get credit for your work. 

Some computer science venues have moved to a model where papers are reviewed and accepted, but the vast majority of papers only get a poster presentation at the conference. Another model is where all accepted papers are invited to a poster session. So it really depends on your area and venue.