lol fail?

http://i.min.us/kkMP70.jpg

Preventing people from downloading your own stuff from your own browser?
Real smart.

Most add-ons are not made from Mozilla directly. I'm guessing more than 95% of them are third party.

If you have doubts of the usefulness of that security feature, I'd be happy to prove you wrong. Security features are there to help you. Complaining about a browser's effort to keep you from fucking yourself over makes you look unintelligent.

How this goes if you do not have that feature:
1. I create decoy page. Make it something that isn't suspicious, like those youtube loop sites. e.g. endlessyoutube.com
2. Include an invisible iframe that loads the add-on I've created. I don't even have to upload it to mozilla. I can do something extremely malicious and load it into your browser without you catching on.

How this goes since you do have that feature:
1. I create decoy page. Make it something that isn't suspicious, like those youtube loop sites. e.g. endlessyoutube.com
2. Include an invisible iframe that loads the add-on I've created. I don't even have to upload it to mozilla.
3. Your browser tells you the page is trying to install an add-on and asks for your permission.