I know all the history books say it was PageRank, but that wasn't the only reason. As I remember things, Google gained adopters as much from its interface being super fast, dead simple, and easily shareable.
Over the course of that year, I saw things get so bad with Y!, that you could sign up for a new email address, and before you could change your opt-out settings, it was too late, the address was sold, and you already had spam in your inbox. That's when Yahoo lost me as a user...
To this day, I have seen decisions of Google that I may not agree with... and others that make me leery in terms of depending on their products/applications. But nothing so sleazy that they've lost me as a user/customer. I know what their business model is... but afaik, they aren't directly selling my information to third parties. This is a pretty big deal.