If they press me for details on this theory (that only happens about half the time) I say that it's as if someone decided to re-invent more and more of Yahoo's popular services in random order, giving them a fresh user interface, less historical baggage, and usually one feature that really stands out (such as Gmail's storage limit or Google Talk's use of Jabber).
Google is Building Yahoo 2.0 (by Jeremy Zawodny)
Yep. That's a pretty good strategy sometimes. Take an existing succesful theme. Copy it. Add a twist ie. do at least one thing dramatically (ie. noticably, addictively) better. And do the rest as well as the incumbent. That's kind of the way nature works, one mutation at a time.
Well, it's only a heuristic. In reality Google tend to do two things dramatically better. Google was two twists on search engines : PageRank and radical simplicity of it's page-design. GMail was two (or maybe three) twists on existing webmail : mega-storage, better interface (and maybe exclusive invites). Google maps is two twists on existing mapping services : amazing interface, impressively hackable. AdSense is three twists on existing ads : context dependence, anyone can join in, unobtrusive.
Twists are useful. They're what get you talked about yet understood. "X is like Y but with Z." They're also what make it hard for users to switch back. "I wouldn't go back to Y now because I'd miss the Z".
Of course, there's no law that says the initial incumbent can't add Z too. But there's less of a message there. Catching up with GMail is not enough to make me switch away.