purpose of two-way communication mirror etc

[Sandra Collins]

No: HPFGUIDX 136038

--- In HPforGrownups at yahoogroups.com, "jakedjensen" 
<jakejensen at h...> wrote:
> That silly mirror that Sirius gives HP in OoTP has been the 
source of a good deal of discussion.
Regulus Black has the other mirror (perhaps found it in 
Grimauld place...perhaps he had another...perhaps he even 
bought it off Mundungus) and will use it to contact HP in book 7. 
> 
> Jake
> 

I was surprised by a 2way mirror being introduced in book 5 after 
all the trouble a time turner caused in book 3, because the last 
thing the stories needed was another plot device that could be a 
loose cannon. If this manner of communication exists, the lead 
characters need never be separated - it's like the WW version of 
a trendy mobile video-phone. And it's a perfect bugging device for 
any dodgy characters to spy on HP and the rest, and vice versa. 
Harry could, under his cloak, have left one in the Slytherin 
common room, and picked up all kinds of snippets of info, or left 
one in Snape's room and so on. The possibilities are endless. 
And that makes me wonder - if the spell exists for the Weasley 
twins to make extendable ears for a little prying, it can't be too 
difficult to perform. So how come the principle had never  been 
adapted by the wizarding powers-that-be to listen in on 
suspected Death Eaters?

Sandra