Since there seems to be some confusion on this point: in canon, at least, an "Unbreakable" Vow didn't actually stop you breaking it, it just killed you if you did. If a person is willing to sacrifice their life - and if you resurrect using a horcrux, that could easily be worth it - you can still commit crimes.
And if you swore to obey the law - is being found guilty is now an automatic death sentence, even if you honestly thought it was legal? I doubt a working legal system based on Unbreakable Vows is trivial to come up with.
That said, they are unquestionably broken in canon. Very, very broken. Few are willing to stake their life over, say, business deals, but there are loads of situations in which they would be a massive game-breaker.
The next discussion thread is here.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 85. The previous thread has long passed 500 comments. Comment in the 15th thread until you read chapter 85.
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: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15.
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: