Hitwise released a report saying Facebook.com generates nearly 1 in 4 page views in the US. It well surpassed Google in terms of in visits and greatly surpassed Google in terms of "page views."
Hitwise said, "The market share of page views for Facebook.com was 24.27% last week, 3.8x the volume of the 2nd ranked website YouTube.com with 6.93%." Google's volume in page views was 5.32%, but keep in mind, Google owns YouTube.
A WebmasterWorld thread has some fun conversation around this latest metric. One person's post, I made the title of this article.
You have to separate "pageviews" from "visits". Every time someone clicks "refresh" in their browser, it's a pageview. I know a lot of people who leave a tab permanently open to facebook, and pop over to it every 10 or 15 minutes and click refresh to see if there's any updates.
It's the crack cocaine of the internet.
Moderator, skibum, added a nice note comparing the value of a Google page view to a Facebook page view. She said in summary, you can see the long post in the forums:
If all these FB pages views were worth something, then forums would be the most valuable properties on the web and be going public at billion dollar valuations.
Forum discussion at WebmasterWorld.