DIATSSISE theory aside, "Spinners End" could also relate to
Snape. If it was
Snape (not Snapledore) and he is evil, it meant that he would have to reveal his evil ways by killing
Dumbledore (if Malfoy failed), and alienate himself from Hogwarts and most of the wizarding world. Or if he is good
Snape, he would still have to kill DD ( if Malfoy failed) and alienate himself from Hogwarts and most of the wizarding world. It could be a clever peice of writing by JKR to keep us in suspense about whether or not we think
Snape is evil, because by taking the unbreakable vow
Snape either has to watch DD be killed by Malfoy or do it himself.
I am hoping that
Snape is good, and the twitch of his hand when Narcissa adds the last part of the vow, is because
Snape thought he was only going to have to swear to protect Malfoy, not to carry out the deed if he failed and so thought 'bugger, I'm either going to have to watch DD die or kill him myself, either way the OOtP will think I'm evil and most of the wizarding world will too!' (sounds a bit like he's put himself in a catch 22 situation to me).
I cant wait to read The Deathly Hallows and find out either way.
The DIATSSISE theory is well written but I just cant see why DD would have to impersonate
Snape to spy on Wormatil, when
Snape is a superb Occlumens/Legilimens anyway.
Snape can 'interrogate' Wormatail, he is a spy for DD and the OOtP after all, and let DD now the outcome.
LV may have placed Wormtail with
Snape because he did not trust
Snape entirely and wanted him spied on to check he wasn’t working for the other side. WT isn’t the best death eater around so it wouldn't scupper LV's plans to have him not doing much.
Plus JKR may have wanted to keep Wormtail in our minds to remind us that he has a life debt to
Harry and a hand that is apparently made from silver, which is a handy weapon against werewolves i.e. Fenrir Greyback..................