That's only true if one has access to data at every point in the block chain. If at some point coins go to a private person or company that didn't advertise th

That's only true if one has access to data at every point in the block chain. If at some point coins go to a private person or company that didn't advertise their address anywhere you're lost. There's no way to know who own a Bitcoin address if it's not part of any online service/exchange and was funded by someone else.