He wrote GMail. It's very common for humans to have a strong enough emotional investment and attachment to the fruits of their labor that they act irrationally in manners involving that creation. Seeing GMail get abandoned by users would be psychologically very similar to (though probably far less severe than) the pain of seeing your child spurned by his peers.
Indeed. As a parent and software producer I can feel the same part of my brain activate when (irrationally) defending my "offspring". I don't think I will change that though ;)
But it's a ridiculous comparison. Has twitter killed RSS yet?
maybe not yet on a global scale, but for me and some people I know, it certainly has. Never open my reader anymore: almost all good links come to me via twitter.