For the Genomics Data Carpentry (that we're just now piloting) we'll be teaching how to log in to and use cloud or high performance computing. In the very first run at James Madison, Stephen and Amanda ran in to the issue that the guest network was blocking Amazon AWS IP addresses.
The workaround was to have someone log guests in to the regular network or to have learners ssh to another server first and then to the Amazon instances. We set up an account on the Data Carpentry server for this purpose.
Mainly though, this is another checklist item for organizers/hosts/instructors that if you're teaching with Amazon or another cloud compute to check to make sure that people can log in from the network they'll be using during the workshop.