Facebook, Messenger, Instagram, and WhatsApp had a massive outage a few hours prior to the publication of this post. This outage affected an estimate of 60% of the userbase and hit the most in Central Europe, England, the east coast of the US and the Philippines. Other countries might have been affected too, but the time zone difference might have made it so that people were asleep during this time.
Facebook states that this was an internal error, not caused by any outside attackers. They apologized for the downtime and gave the all clear on their systems today at around 9 AM eastern time.
Steem has had a few occurrences of DDoS attacks held against the main website steemit.com which however never affected any users on platforms other than users accessing the blockchain through that particular site. The benefit of steem is that it is exponentially harder to take it down with DDoS attacks, as you have to hit multiple witness accounts at a time, and even then there are accounts ready to stand in.
I believe steem is a revolutionary platform with much good to come.