Comment 4 for bug 147807

"The maximum default cluster size under Windows XP is 4 kilobytes (KB) because NTFS file compression is not possible on drives with a larger allocation size. The Format utility never uses clusters that are larger than 4 KB unless you specifically override that default either by using the /A: option for command-line formatting or by specifying a larger cluster size in the Format dialog box in Disk Management. "
  -- http://support.microsoft.com/kb/314878

That also has the following table:

  Drive size
   (logical volume) FAT type Sectors Cluster size
   -----------------------------------------------------------------------
       15 MB or less 12-bit 8 4 KB
       16 MB - 127 MB 16-bit 4 2 KB
      128 MB - 255 MB 16-bit 8 4 KB
      256 MB - 511 MB 16-bit 16 8 KB
      512 MB - 1,023 MB 16-bit 32 16 KB
    1,024 MB - 2,048 MB 16-bit 64 32 KB
    2,048 MB - 4,096 MB 16-bit 128 64 KB
   *4,096 MB - 8,192 MB 16-bit 256 128 KB Windows NT 4.0 only
   *8,192 MB - 16384 MB 16-bit 512 256 KB Windows NT 4.0 only

Also see:

"As versions of Windows NT earlier than 3.51 do not support NTFS file compression, the default cluster sizes will go above 4k."
  -- http://support.microsoft.com/kb/140365

So it seems that FAT itself goes up to 256KB sector sizes -- but that usually Windows prefers you to stay at 4KB or below.

vol_id should still probably support the larger sector sizes, especially if disk makers are formatting with them against Microsoft's recommendation.