This kind of bundling is often done by the bad guys. If you install Apple’s Quicktime codecs on Windows every update will trigger an iTunes install, even if you haven’t installed iTunes. I’m sure they’ll do the same thing for Safari on Windows. I’m not sure what iTunes’ market share on Windows is but it seems to be significant. If all those users suddenly have Safari installed that could potentially cause a big shake-up in browser market share.
On Friday there was a minor shitstorm on planet.mozilla.org about Apple pushing down Safari to all Windows iTunes and Quicktime users.
If only we had a reusable system-wide XULRunner it would be really easy to do similar but less evil promotion of our growing XUL-based free software suite. Songbird could suggest to users that they might like Firefox - and it would take just a single click and a tiny XPI download to have users running Firefox. We could even get intelligent and suggest Thunderbird to heavy email users or Flock to heavy social networking users.
iTunes' US market share is around 27% (according to the best numbers I can find). If Apple flips the switch and makes Safari the default browser for all those users Firefox will start looking irrelevant fast.