Abandonware site charges for downloads

Everything is still owned by someone, unless it has been explicitly placed into the public domain by its last owner. AFAIK, the concept of "abandonware" doesn't have any legal basis whatsoever. It may well be the case that the ownership of old software can't be determined, because the records were lost as ownership changed hands many times between then and now. The current owners may not even know that they own it. This is a fundamental problem with US copyright law. With tangible property, when a dispute arises the property owner has to prove ownership (via a title document). With copyrights, if Joe claims that Bob does not own a work, it is up to Joe to prove that claim, and the legal presumption is that Bob *does* own it. For "abandonware", anyone could come forward and claim to own it, and it would be difficult or impossible for such claims to be disproven. (Perhaps someone may see this as an opportunity?)