throw HIMSELF off the topmost tower

[n_longbottom01]

No: HPFGUIDX 144209

Something Dobby said at the end of the "Elf Tails" chapter (p. 422 
U.S.) of Half-Blood Prince sparked an idea for what might have really 
gone on at the top of the Lightning Struck Tower.  Here's the quote:

"And if Dobby does it wrong, Dobby will throw himself off the topmost 
tower, Harry Potter!"

When House Elves fail their Master, or betray their Master's 
confidences, they are obligated (as a part of their nature, in 
combination with the magic that binds them?) to punish themselves 
physically (bash their head into a desk repeatedly, etc.).  Dobby is 
a free elf, and is under no obligation to punish himself for failing 
Harry Potter, but he chooses to express his loyalty to Harry by 
saying, in effect, that he will treat Harry's request as if it were a 
request from a Master to his House Elf.  And to show the extent of 
his loyalty, Dobby doesn't just say he will slam his hands in a 
drawer if he fails, he says he is going to throw himself off the 
tallest tower in the castle—the same tower that we later see Snape 
blast Dumbledore off of.

Dobby's statement that he would "throw himself off" the tower made me 
wonder, was Dumbledore thrown off of the tower because of his 
failure?  Or did Dumbledore, in effect, throw himself off of the 
tower in an act of loyalty (and self-sacrifice)?

Here's my best case scenario for "Good" Snape.  Dumbledore, realizing 
that there was no other way out of the situation he was in, uses 
something along the lines of the Imperius Curse to momentarily take 
control of Snape, and against Snape's will, uses Snape to cast the AK 
that blasts Dumbledore off the side of the tower.  This might make 
Dumbledore seem a wee bit ruthless, but it saves Snape, Draco, and 
possibly other lives (Snape's life because of his Unbreakable Vow, 
Draco's life because Voldemort won't kill him for not completing his 
assignment, and other lives because Snape is then able to hurry the 
Death Eaters out of the Castle).

Dumbledore didn't have his wand any more by the time Snape appeared 
at the top of the tower, but it is brought to our attention at least 
once in the story (when Harry is frozen and bleeding on the Hogwarts 
Express) that Dumbledore is capable of doing wandless magic.  I could 
go either way on this point
 maybe the fact that Dumbledore doesn't 
have his wand nixes this theory, or maybe he is able to Imperius 
Snape without using a wand.

I'm not sure that there is anything to this (and I apologize if this 
theory has been stated a million times before).  I don't know what to 
make of Snape
 I'm on the fence.  But, if Snape is going to turn out 
to be an all-around good guy, then it is more satisfying to heap more 
of the blame for what happened onto Dumbledore
 I'm ok with 
Dumbledore using Snape to off himself, because it saved Snape's life, 
even if it did make him look like a murder.  I can't entirely warm up 
to the idea of Snape just agreeing to kill Dumbledore, if need be, no 
mater what was hoped to be accomplished by such an agreement.

n_longbottom01