Another example was when Anonymous decided to start outing Cartel members. They kidnapped one of the people involved and Anonymous declared a truce to get that person released.

source: http://www.nydailynews.com/news/world/member-anonymous-relea...

Here's one example. Googling for something like "cartel kills social media activist" will probably yield more.

http://techland.time.com/2011/11/10/fourth-blogger-reportedl...