Obviously, it was a slightly tongue in cheek comment..
However, I would point out that WebMynd IS doing personalised search (totally personalised, in fact). As you point out, updating search indices every time a user visits a page is difficult. The fact that Google have chosen not to tackle this challenge, and we have, is a symptom of their existing methods and stated goal of organising the world's information: not your's.
As for your last point, I actually agree with the OP and others that Google's soft touch on this matter was commendable; disabling the effect or blocking the extension outright would have been heavy handed and sent a pretty bad message.