Well I sent a request asking what was up earlier and got this response.
"SHELL tripped one of our internal security alerts, it is now back online as everything checked out fine."
So whatever that means lol
That's really absurd

did this happen before, they should post a clarification. They just scared people away for no reason at all.
At any rate I will have an announcement tomorrow that will surprise most of you and put SHELL on the right track again.
Never heard of this happening before, it's a bit weird but it's back now so that's the good thing.
Look forward to the update
Poloniex has a similar automated mechanism. If someone deposits a large percentage of a coin's distribution then all trades are automatically frozen until one of the staff can verify there is no funny business going on.