Oh god I love your Imperius idea. Although the sense I get is that Imperius is very hard to cast and powerful wizards can resist, so a) it wouldn't necessarily be an effective virus, b) it might be pretty easy to notice and then counter, if you were too obvious about it.
Not to mention, if you lost one person, then everyone they infected, and those they infected, ad nauseum, would be released.
You could try to mitigate that by having overlapping vectors of infection, but I'm not sure how someone would react to having multiple Imperiuses cast on them.
Update: Discussion has moved on to a new thread.
The load more comments links are getting annoying (at least if you're not logged in), so it's time for a new Harry Potter and the Methods of Rationality discussion thread. We're also approaching the traditional 500-comment mark, but I think that hidden comments provide more appropriate joints to carve these threads at. So as of chapter 67, this is the place to share your thoughts about Eliezer Yudkowsky's Harry Potter fanfic.
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. The fanfiction.net author page is the central author-controlled HPMOR clearinghouse with links to the RSS feed, pdf version, TV Tropes pages, fan art, and more, and AdeleneDawner has kept an archive of Author's Notes.
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: