ON its Web site, Facebook says it’s “giving people the power to share and make the world more open and connected.”

But the online world outside of Facebook is already a very open and connected place, thank you very much. Densely interlinked Web pages, blogs, news articles and Tweets are all visible to anyone and everyone. Instead of contributing to this interconnected, open Web world, the growing popularity of Facebook is draining it of attention, energy and posts that are in public view.

Every link found on the open Web, inviting a user to click and go somewhere else, is in essence a recommendation from the person who authored the page, posted it or broadcast it in a Tweet. It says, “I’ve taken the trouble to insert this link because I believe it will be worth your while to take a look.”

These recommendations are visible to search engines, which do far more than just tally how many recommendations point to this or that item. The engines trace backward to who linked to the recommender, then who linked to the recommender of the recommender, and so on. It’s a lot of computation to derive educated guesses about which recommendations are likely to lead to the best-informed sources of information and then placed at the top of a search results page.