What are some of the challenges that could arise from setting up a file management system on a computer?

Setting up a file mgmt system on a computer could simply involve placing files in appropriate folders to separate different categories of files like say photos of different subject matter. A challenge might be deciding what files to put where as some of them may have affinities for another topic as well so clear criteria would have to be made as to the content of each folder. Also, like say a folder with invoices it would have to be decided if the invoices would be shown for the whole history of invoices or separated into years.