You may run into compliance issues, although it probably depends on your use case. For example, what do you intend to do with the stored data? Compile aggregate information? Publish it online? Is your biz model encouraging eBay buying or selling behavior? Unfortunately, I don't have any clear cut answers for you; sorry. I'm just making the general point that use case is important here. You may want to reach out to the eBay Dev team and try to get some clarity from them.