I'm not sure if there is an official explanation but a pretty good analysis of it is in John Siracusa's review of OS X 10.7 (Lion): http://arstechnica.com/appl

I'm not sure if there is an official explanation but a pretty good analysis of it is in John Siracusa's review of OS X 10.7 (Lion): http://arstechnica.com/apple/2011/07/mac-os-x-10-7/12 http://arstechnica.com/apple/2011/07/mac-os-x-10-7/12 http://arstechnica.com/apple/2011/07/mac-os-x-10-7/13 http://arstechnica.com/apple/2011/07/mac-os-x-10-7/13