Hi, Jeremy!
Just read through your post, and no one can argue that Google's important - but putting all your eggs in one basket, any basket, can spell doom before long.
18 months ago there were a lot of people saying you only needed AltaVista to succeed. Now it's Google. Next year it will either be the new Yahoo-owned network or the new MSN crawler.
The Florida update at Google is a prime example. With no change in our links, content or tags, that one change took us from page 1 for web site marketing to off the scale - even though we'd been first page for over 3 years! Fortunately, while this did hurt, we have a number of other engines sending us traffic, plus what we get from inbound links. And it wasn't that we were spamming the engines - 3 of our other sites are still generating over a million pageviews a year optimized the same way.
Google has remained very quiet about why so many sites dropped under all sorts of categories, while other areas stayed level. One theory that seems to be gaining supporters is that the PageRank algorythm may still belong to Stanford, meaning Google would drop it before their anticipated IPO this year. Since many of the sites dropped had a LOT of incoming links, this may just be why.
Just for a minute, assume a cosmic beam erased Google tomorrow, or that they turned out to be another Enron (which they aren't, but just for illustration). Our sites would still be profitable - would yours?
Hope it helps,