Just a quick thought about manners in general, but specifically on social media. This could easily apply to the idea of how to engage in any conversation.
I recently stopped to take a look at the arguments that occur on Facebook, including the ones in which I've partaken (or even started). My thoughts while examining this was comparing those incidents and participants with the number of times I engaged with pleasantries. How often did I write on their wall for birthdays, anniversary or just to be uplifting? When was the last time I engaged with friends for socially-acceptable social media? Did I know them well enough to post a funny thing related to their life or something about their interests or hobbies?
I was appalled (and disappointed in myself) of how often I would argue with someone I barely knew -- or feel the need to interject my opinion about a topic just because it caught my attention. If those same threads had pictures of cats, family members or their recent vacation...well, I'd probably have stayed silent.
As one person phrased it, how would we explain to our forefathers that we have advanced to where all the world's knowledge can be accessed from a small device in my pocket, but I use it to view pictures of Cheezburger Cats and argue with people I don't even know. ...food for thought.