Is Big Brother Watching? (about the MoM)

[Jenny]

No: HPFGUIDX 54752

What is it that allows the MoM to ascertain when and where magic is 
being used?  And, if they can detect magic, why can they not tell 
*who* is doing the magic? Some interesting points to note from the 
books:

In CoS, the MoM dispatched a letter to Harry mere minutes after a 
Hover Charm was used in the Dursley home. However, it wasn't
Harry who did the spell, and the MoM seemed unaware of this fact. 
(Possible answer: one of a house-elf's powers?)

In GoF, Ron talks about the mysterious explosions that have been 
coming from F&G's room for some time.  Now, granted, canon does
not directly say F&G were using magic, so the possibility lies that 
they made potions, but Ton-Tongue Toffee was made with an Engorgement 
Charm, and unless they made it at Hogwarts before they left for the 
holiday, they used magic at home to create it. Yet no letter was 
delivered to the Weasley home from the MoM regarding this.  Is this 
perhaps because the Weasleys are a wizarding family and it was 
unknown that an underage wizard did the spells? (Refuting the 
possibility of making it at Hogwarts before holiday is the obvious 
point that if they had, why didn't they "test" it on a
student at Hogwarts?  And since they'd been waiting to use it all 
summer,Bill or Charlie could not have done the charm for them since 
they had not been around all summer)

Just how does the MoM keep track of underage wizards from wizarding 
families if they cannot tell who is doing the magic?  Is there any 
way to tell an underage wizard has used magic?  This whole area seems 
uncharted territory and I wonder how J.K. plans to explain this.

We know they keep tabs on people who apparate as well, as described 
in GoF when Mr. Weasley talks about the couple unauthorized to 
apparate who splinched themselves.

Knowing those things, how are they unable to detect when, say, 
Voldemort kills Bertha Jorkins or the old man at the Riddle house? 
And how did they not know Moody!Crouch killed and transfigured his 
father at Hogwarts? (Possibly, Dark Magic is hidden from their 
knowing?)  But then, does this explain how Dumbledore knew so quickly 
the Potters had been killed?
 
I know there are other such examples, but those are the ones that are 
currently standing out in my mind.

J.K. Rowling said in an interview with Raincoast Book in March 2001 
(interview is on muggle.net) that "Wizards don't really need to
use the Internet but that's something that you'll find out later on 
in the series. They have a means of finding out what goes on in the 
outside world that I think is more fun than the Internet."  Now,
I'm not sure if by "outside world" she means the muggle
world or
just the world outside in general, so I don't know if this is 
relevant to the topic.

If this has been discussed before, I'd love a point in the
direction of the posts so I can read them!

Jenny, who is very happy to have found this group :)