No doubt the notebook processors were a big reason why, but free Linux is eating *nix's lunch in many cases, and that includes OSX. Solaris can now go toe to toe on Intel, and so will OSX. Not sure how you never understood what was going on, when two of the most well known journalists covering Linux and Apple were all over it.
http://www.eweek.com/article2/0,1895,1824810,00.asp
http://www.marketwatch.com/News/Story/Story.aspx?guid=%7BD0E8469A%2D28FC%2D415D%2D9281%2DC97B5FA2CA3D%7D&siteid=mktw&dist=nbs
You mean Mr. "I've been becoming increasingly unhinged lately" Dvorak?
Linux is nowhere a danger to Windows or OS X on the public desktop for the near future. The user experience is too fragmented for Joe User. If it were warranted, Apple had ample opportunity to be afraid of Linux already since Linux has been running on PPC for a while. Linux Torvalds' preferred machine is Linux on a PowerMac.