Nature of the Vow:

[Ceridwen]

No: HPFGUIDX 145462

Wink45:
> We have already seen an Unbreakable Vow broken, and the results.  
> Hermione set one on the list of the students who signed up to be 
> part of 'Dumbledore's Army.'
*(snip)*

Ceridwen:
That was not an Unbreakable Vow.  The vow in 'Spinner's End' was very 
ritualized.  Get onto knees, hold hands, a third party listens to the 
conditions of the vow and the agreement to them.  As each condition 
is stated and agreed to, a red magical cord comes out of the binder's 
wand and ties the parties' hands together.  This continues until the 
vow is finished.

Hermione set a spell on a parchment (or its quill or ink) and said 
that if they signed, they were agreeing not to tell Umbridge, or 
anybody else, what they were up to.  (OotP pg. 346, highly 
paraphrased).  It was definitely a vow which was sealed by signing 
the parchment (with that quill and/or ink?), but it was nowhere near 
as ritualized as the UV we saw in 'Spinner's End'.

But, for vows with consequences, the one Hermione snuck onto the DA 
members is a good example.  By signing, they agreed.  And by breaking 
it, Marietta wound up with a brand on her face.  Which is the penalty 
Hermione inserted into the vow.  I probably shouldn't think about 
this too much, because Hermione comes off as sneaky and manipulative 
in this scene.  In fact, in this business and its aftermath, I don't 
care much for Hermione at all.

Which, of course, makes me wonder what wording Fred and George used 
when they tried to get Ron to take a UV.  Did they say '...or die 
trying', or something similar?  Could that be why Arthur got so mad?

Anyway, they're probably both part of a larger group of magical vows 
which have consequences to greater or lesser extent.  The UV's 
consequence is, *IMO*, that the person would not be able to break the 
vow even if their feelings changed.

Ceridwen.