Yes, well, your average user isn't going to bother with that for every web site to make it usable with Firefox. And there's a good chance that MS's Atlas toolkit will integrate the non-IE-degrading functionality in such a way that disabling it will disable all the AJAX functionality.
the libervis link you provided has this titbit - if you use firefox, and for some insane reason find yourself needing to go to msn.com, try using the adblock extension, and block this file: http://hp.msn.com/scr/home/msnmoz1021.js
robert's yr mother's brother.
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