All eyes are on steem right now. There was a temporary problem with the chain.
You probably are going to hear about this a LOT over the next couple of days...
Yes, it is true, the steem blockchain was paused. It did that because witness nodes couldn't reach consensus on what blocks were valid.
This happened at exactly the right time, right when witnesses were transitioning from version 0.19.6 / 0.19.12 to the new 0.20 version of the blockchain.
There was a small glitch, that made 0.20 software not 100% compatible with older 0.19 witness nodes.
Before I continue, I must explain, these are my observations and opinions, and in no way should be taken as official word or facts. Please investigate yourself, or wait from official word from Steemit.
It was a tiny mathematical inconsistency that was present in 0.20 and merged July 18, 2018. (here)
It made it through testnet "just fine".
It even made it through "mainnet" just fine.
Actually both older 0.19 witness nodes, and 0.20 witness nodes were working as intended, just fine.... on the main live chain for many days, without issue.
Until the right time hit, where someone did a 0.20 vote that certain witnesses accepted, that older 0.19 witnesses didn't agree with... and at that point, things got fragmented really quick. It seemed that the chain lost consensus, all at once.
The quick response (and believe me, same day fix is fairly quick)... to track down the problem, implement fixes, test those fixes, and get witnesses back online again was pretty fair... especially if you understand "decentralized software development".
During the outage, I heard people complaining about "software needs to be perfect."
I agree...
But ask yourself, when is the last time your computer needed an emergency update? Or your antivirus software? How about your phone?
Ever hear about a bank glitch? Ever see a TV station not broadcast properly?
In a software world, unexpected things will happen. Especially when programming code gets complicated, and there are more and more lines of code to examine.
The best thing you can do, when a problem like this arises... (and there may be others in the future)... is to keep calm. Be supportive, and communicate to others if you know something they might not.
....and that's the reason for this post. :)
Since I am not on the development team.... nor am I privy to the steem slack... I had to obtain my information through my own research and by participating in steem.chat.
I also run a witness node, named 
I should also mention that other networks, like whaleshares were not effected by this particular outage, because they are running similar code with significant differences on a different fork.
- ...and that's the benefit of different blockchains, and open source code development. Dan Larimer was brilliant when he insisted that steem should be Open Source, just like Satoshi Nakamoto did with Bitcoin. :)