Eh, she is a first year at hogwarts - from their perspective, what is she going to do with it? Apparate out?
Just because they don't expect her to be able to accomplish much with it doesn't mean that they wouldn't stop it as a matter of policy. You don't let a character witness walk up and hand anything to a prisoner on the stands without clearance.
A whole lot of plans proposed here seem to rely on the assumption that Harry can treat the Wizengamot as a captive audience who'll humor any attempt he makes to sway them or prove his points. The Wizengamot is a highly authoritarian court of law, and Harry is a first year student. They have little incentive to humor him about anything.
EDIT: New discussion thread here.
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. With two chapters recently the previous thread has very quickly reached 500 comments. The latest chapter as of 17th March 2012 is Ch. 79.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author's Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight, nine, ten.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: