I remember the Loma Prieta earthquake of 1989. At the time it happened, I was in People’s Music in Sebastopol and all of a sudden, the guitars were lightly swinging on the walls. I went outside, and the telephone pole wires were bouncing up and down. Aside from that, it was pretty mild and so I just went home. Then I turned on the news. Wow! San Francisco was on fire, the Bay Bridge had a big chunk missing and the freeway in Oakland had collapsed!
For many months after, the Bay Area slowly recovered, it’s infrastructure having been heavily disrupted by the quake. Merchants in the SF Embarcadero near the bridge found that one of their main sources of traffic had dried up. Cars simply couldn’t exit the bridge. No traffic, no business.
And so it is with Google for websites. If one day, your site winds up on page four when it had been on page one, you’re going to wonder where all the traffic went. What’s worse, there’s not much you can do about it. So dominant is Google’s share of search, that there really isn’t anything close to turn to if for some reason your site takes a big drop. For some sites, that could be all it takes to put them out of business. For others, it just means getting used to the new position and working just that much harder on the quality of their site. With no eye towards Google, or being in any way reliant on its whims.