A C&D like this is pretty standard fare between competing businesses. If you sell widgets and WidgetCorp sells widgets, you are completely allowed to try and poach their customers, but WidgetCorp is allowed you prevent you from doing that in their store. Furthermore, if the accounts were specifically created for this purpose it's a clear violation of the TOS and there may potentially be damages there, or even possible criminal charges (thanks to the wonderful CFAA - ack).
Asking the courts to enforce a cease and desist seems fairly reasonable (perhaps a bit heavy handed), but I absolutely disagree with the idea the courts should impose monetary damages on Amazon for using eBay's website 'improperly'.
In your example, it'd be reasonable for WidgetCorp to trespass you from the store if you're trying to compete on their property. However, I believe it would be unreasonable for Widgetcorp to try to sue for the revenue of the sales that were successfully made before they trespassed you.
A C&D like this is pretty standard fare between competing businesses. If you sell widgets and WidgetCorp sells widgets, you are completely allowed to try and poach their customers, but WidgetCorp is allowed you prevent you from doing that in their store. Furthermore, if the accounts were specifically created for this purpose it's a clear violation of the TOS and there may potentially be damages there, or even possible criminal charges (thanks to the wonderful CFAA - ack).