It can get really hard to tell where the line is, though. For example, multiple for-pay third-party clients for Google Music now exist [0]. Personally, I think this is still a value-add for Google, but I could understand why some would think it's exploitative.
Another thought experiment: say the unofficial use of the platform originally required a fair amount of reverse engineering. Can the person who figured it out be held responsible for other's abusive behavior?
But then I'm not sure still...maybe that is okay if consumers massively benefit from the reverse engineering, and thus overall utility is increased...! What do you think?
Generally, though, I think the situation has interesting parallels to piracy. Companies have many options on how to respond to unofficial use:
- cracking down on unofficial users == chasing down pirates
- attempting to control unofficial use (probably at the cost of normal usability) == DRM
- embracing unofficial users == the "piracy as free marketing" view
- viewing unofficial users as a sign of a specific weakness in the product == the "piracy as a service problem" view
I suppose that would make the original reverse engineer similar to someone who cracks a game's DRM?