Signing a petition for a fault to be corrected like the faulty AGC (Automatic Gain Control) with its top-end HISS, in the EOS 550D -- which can't be disabled -- is a very cap-in-hand way of telling Canon that they actually have a choice in the matter.  If you purchased a new car with an exaust so noisy that the vehicle was lawfully unusable would you simply sign a petition--or tell the manufacturer to take the 'lemon' back and fix it?
It's not as if AGCs are a new problem. These things have been causing problems in video equipment since the 80s.
Yes, I have my own fix, which is to extract the audio in a video editor and run it through an old version of Cool Edit (V2) -- choosing Effects/Noise Reduction/Hiss Reduction/Standard Hiss Reduction. And you get most of it out (with some very slight 'breathing' after a period of silence just before the next passage of audio). But it's time wasting and isn't perfect and shouldn't be required in the first place. And it's an anachronism that 18-year-old software can fix a problem that the 2009/2010 Canon EOS 550D camera creates.
What is more ridiculous is that if Canon's audio guys (presuming they have such staff) were incapable of putting a decent AGC in the camera, and for reasons known only to them left out a 'disable' function, then they simply could have asked some first-year apprentice audio technician  how to put a filter with a cut-off frequency on the damn thing.
I've written to Canon, but if they can't rectify the problem I'm taking the camera back as 'faulty' and asking for a refund.  I'm not interested in third party hacks that void the warranty.

I think the big point is: It's a DSLR not a videocamera! Those things are originally built for fotopgraphs! The Videofunction is "just" a nice feature. And i don't think you can claim refund, because it is not "faulty". It works how it is ment to work. In a Car (take on your comparison) you also can't disable ABS, although it is very disturbing when you want to drift around a corner.
If you want good audio recoding get a Zoom h4n or something similar beacuse those devices are built for recording high quality audio.

I should have been more specific with the external device I was referring to.  Yes, external audio in itself is a solution too, but I was actually talking about devices like these:

http://www.bhphotovideo.com/c/product/672399-REG/juicedLink_DN101_DN101_Automatic_Gain_Control.html

Seriously?

You're complaining about ACG?
This camera has a more serious problem then ACG!!

I've sent my camera 3 times to Canon and once to Canon CPS (Canon Professional Services) and the result is... "our camera does the same thing, there are no fix..."

The problem?... After you set some settings, the camera's display "randomly" stays off when you turn it on. Basically C.FN (Custom Function) 11 "LCD display when power ON" does not work as advertised! This can confuse you in thinking that the batteries are dead.

Search youtube for "t2i display problem"

WowTask! I was thinking it was all in my head. Yes I have that same issue from time to time but I have never put together what makes it happen.

Just press the LiveView button when this happens...

You think I didn't thought about that? Of course I can press the Live View or Disp. button everytime, but that defeats the purpose. I don't want to switch on the camera then turn on the display everytime!

The camera should work as advertised on pg. 196 of the Instruction Manual. "When the power switch is turned on, the shooting settings will be displayed (p.44)"

Worth stressing, probably not. However, I agree that it should work the way they say it should. I have come pretty close to returning mine as I didn't put two and two together and come up with what Task said. I still don't feel it is right that it happens but it isn't going to kill me.

What's with this, "is it on or not" stuff?  The red light indicates when activity is happening and you just press the LiveView button if for some reason the screen is still black after turning it on.  I never have problems knowing whether or not my battery is dead.  Auto shutoff or whatever should be disabled anyway.  Why would you want that enabled if you're the type of person that's posting on these forums?  It's like complaining about no autofocus.

I'm pretty sure ML is getting close to fixing this anyway.  There's been new settings to play around with that force LiveView and stuff that I haven't messed around with yet.  Mainly because I don't have any real problems.

You say every time you're about to shoot something you cannot determine whether or not the battery is dead because you have auto-off set and I'm guessing you walk around for a bit before you decide to take a picture of something.  Well honestly, just change your habits.  You should have your camera on and ready when you're actually taking pictures or whatever.  If you're letting your camera automatically turn off, maybe it wasn't a good time to take it out in the first place.