New OS X uses Windows file sharing by default
> Time Machine, only works over a LAN with destinations that support AFP. This is at least in part because of Time Machine's reliance on Unix hard links, and also in part because it has to be able to ensure that any OS X files with HFS+ specific metadata are correctly preserved.This is not the reason.  Time Machine does support hard links, legacy Mac metadata, and other Unix features.  It does this by writing all the data into large blobs (a sparse bundle) with an embedded filesystem of its choosing (i.e. HFS+). It can use any destination filesystem for the blobs, including FAT.