Sorry for the very newb question, but is it simple to remotely control SmartThings. And when I say remotely, I mean while not on your local network? Can I login while on vacation and update settings? Is this a security nightmare, etc? Thanks.
yes - via a smartphone app. That app talks to the ST cloud, and the cloud talks to your hub.
Thank you. One more question (well that is a lie as I have hundreds, but for now)…
Do all actions route through the cloud? Will my home automation work if my Internet goes down? I think it will still work, but would like some confirmation. I am guessing the ST cloud is just for the smart phone app and maybe a few other functions (ie. backup ST config?).
Thanks!
In the current version of the SmartThings hub, it is reliant on the ST cloud for everything. If internet is down, you will not be able to use the hub to send commands to your devices. It has been strongly hinted that V2 of the hub will allow some local processing to retain control during internet outages. V2 is expected to be announced at CES this week (possibly tonight during the keynote that the CEO of ST will be on stage for).
For those with deeper pockets and worries about connectivity you can also have a cell connection to the cloud which almost 
never goes down.
Actually, cell data service outages are not that uncommon. There’s no such thing as 100% reliable network. Even 99.5% reliability equals ~44 hours of down time per year.
Seems silly to have to go to the cloud in order to communicate between all local devices. Actually more annoying that silly.
Would my Verizon wireless unlimited data plan make this achievable?
@geko Certainly true for some areas. I work for a large telecom outside the US and we run in the 4 9’s for uptime and get pretty close to that. YMMV 
I think the reliable connection here is more related to the ST downtime than the actual IP path.