Nothing is "subject to ESIGN rules" until you want it to be subject to ESIGN. The need to operate under ESIGN rules is triggered by your choice to use electrons instead of trees, and governed entirely by the federal law/reg that requires delivery of the "written" information you must get into the hands of a consumer. You can have differences like Randy cited because the different consumer regs evolved (from "paper only" to "paper or electronic") the way they did.
ESIGN functions more like a license than a regulation. It makes a lot more sense when you compare it with your drivers license. Nobody's required to learn the rules of the road unless s/he chooses to drive on the highway. Likewise, nobody needs to learn ESIGN's rules unless s/he chooses to use the electronic highway as the medium to make federally-regulated information deliveries to consumers.
_________________________
...gone fishing.