LOL, I thought it was
I remember when we talked once you were concerned about backing up your machines and drives to one TM drive, not wanting to mix the backups all together. Just wanted to set things straight.
You mentioned above a 2nd TM external, and partitioning one drive for 2 TMs. One drive/one partition would do it. The TM backup for each machine would have its own separate backup archive on the drive. He can back up all three machines to one HD.
I have one customer that has 7 machines all backed up wirelessly to one drive, each has its own separate sparsebundle with a backups.backupdb folder in each sparsebundle.
At home I backup my laptop wirelessly to the same drive as my mini's attached USB TM drive. The laptop has a sparsebundle since it's done wirelessly, the mini has the standard backups.backupdb folder right on the top level.
Also in your case of multiple drives in one machine each drive would have it's own separate archive folder inside the backups.backupdb folder.