That makes no sense. If a copy of Office 2008 for OSX installed Windows Media Player to fight off iTunes then slashdot would melt from the outrage.
Dammit, quite giving ideas to Microsoft's marketing department!
Besides, something close to this already happens. Microsoft's Office Updater and Adobe's Updater make offers of frivolous add-ons in addition to legitimate updates. This falls nowhere near all the bad behavior Real has committed on people trying to get the free version of Realplayer. And think of all the websites that try to gather unnecessary personal information and/or try to automatically enroll you to their email lists when you register on them? Apple is perhaps being a bit less well-behaved than they were before, but they aren't doing anything close to bad enough to provoke the level of outrage I'm seeing.
If you have the intellectual capacity to uncheck the pre-checked email subscriptions on web page registrations then you will not be "tricked" into downloading Safari. If you are so duped, then you have lost a tiny amount of bandwidth and the temporary loss of some hard disk space, but otherwise encounter no harm whatsoever.
While I do think that Apple is being a little pushy, I believe that this will have the effect of taking users from IE, and won't take users from Firefox. After all, Firefox users have already been proactive about switching their browsers, and the Safari promotion seems to be targeted at people who might switch if it is made very easy for them. At worse, this may take a fraction off the top of Firefox's future growth, but won't slow it down very much by any means.