One might say that the hardest thing about social media is figuring out the privacy settings to make sure anything embarrsing isn't made public. But I don't buy that argument anymore - as social media sites have made it quite easy and given multiple ways to configure privacy settings. There have been enough high-profile cases of grandiose online humilations with resultingly horrible repercussions from posting inappropriate things for people to know the importance of not making one's online life entirely public.
But to be fair not all social media gaffes arise from people making their account public, some inappropriate material is posted or leaked by people within one's closed social network. As in "friends" posting pix of their friends in compromising situations without permission. So one could say the hardest thing about social media is knowing who to trust.
I do think this is a legitimate concern, but social media sites have made it easier to have offending material untagged with one's name or removed. Norms are starting to change (at least among older users - likely not amongst teens) that posting dubious material about a friend is not funny. Admittedly, there is a long way for both companies and users to improve in this regard.
I think the hardest thing about social media is not posting something you direly want to, but that may return to haunt you.
Case in point, over the years I have been treated unprofessionally by some companies and people and there is no viable way to get justice through official channels. Social media and user-generated content sites can be an excellent source of retribution (and maybe even dishing out deserved revenge). A hotel I once stayed at added lot of charges to my credit card and would not reverse them. It was only because I posted a scathing review about this on TripAdvisor that I got a refund. Similarly, I had the worst customer service experience if my life with Bell Canada trying to get their Fine service installed - official complaints got me nowhere, but it pleases me to no end that my blog post on their lousy service gets thousands of views regularly.
But in these cases the opportunity for the companies to strike out against me was minimal (or at least I hope so). So although a desire to post something can be profound and the motivation just, there are cases where doing so may cause you more harm than good.
People might think they are protected by sites that allow anonymous posting. But here's another hard thing - the Internet is never anonymous.
First, it is possible to discern an identity by the nature, style, and date of what someone wrote. Secondly, via IP tracking and other means it is possible to uncover people.
So even when you are seething with righteous injustice and no official channels are open to you, consider carefully - and give yourself at least a week's worth of reflection time - whether it is ultimately best for you to post something. Assume that what you are considering posting was read by the person (e.g. a boss a friend) or the worst person you can think of to read it (future boss, CEO) and that it was known to be by you. Because this can and does happen.
Revenge may be a tasty dish, but it may cause indigestion that repeats on you in unpleasant ways. So the hardest thing about social media is not posting something that really needs to be posted.
It's better to seeth privately with injustice of my treatment, than to let a few minutes of venting (however blissful they may be) result in long term damage to you. Instead repress your rage by watching cat videos or filling out online personality quizes until the seething passes.