Another Google algo update and, as ever, original, interesting, useful content is key to SEO success.

The hit eBay’s taken is interesting, though… An 80% drop in Google traffic coukd be a business-killer for anyone less big. And their content surely *is* original and relevant, what with the products changing all the time?

Possibly another impact from the authorship/Google+ changes the Google guys have introduced? After all, eBay product page writers are hardly likely to be verified Google+ authors. Is this why eBay are starting to invest in creating narrative content around their auctions?

Update: See also the ever-excellent Matthew Ingram on this, who points out the extremely worrying hit the long-running and much-loved Metafilter has taken:

“Reliant on Google not only for the bulk of its traffic but also the bulk of its advertising revenue, Metafilter has had to lay off almost half of its staff.”

The lesson?

Google can kill a site on a whim, and even the experts can’t tell us how or why, because Google’s algorithms are even more secret than the Colonel’s delicious blend of herbs and spices. Any site dependent on search for the bulk of its traffic is playing a very, very dangerous game.

Update 2: More detail on the Metafilter revenue/traffic decline, complete with stats.

The related power of Facebook to stifle updates from sources it has deemed to be suspect for whatever reason simply – and even the New York Times’ recently-leaked innovation report’s charts In the decline of its homepage – makes an obvious cliché all the more true even it comes to Web traffic: don’t put all your eggs in one basket.

If more than 25% of your traffic/revenue comes from one source, you’re in danger. More than 50%, you have a potential death sentence. All it takes is one thing to change, and you’re screwed.