In example downloading images always means to keep track from where you got it in case you need more images from the source or because of legal aspects. For example I’m a big fan of icons and collecting them for private use when they are something special. The simplest way is collect them in folders for every website. Better would be to store the information in the metadata of the file itself.
When saving attachments from an email to the local hard disk the email client should also embed the sender email address in the local file. A lot of document types allow storing this kind of information. I think to rely on an application to keep track which document originates from which email is the wrong approach.
The reason why:
- when downloading images from e.g. stockphotos they often don’t contain the original website. In case you want to find more photos of the same at a later time it’s easier with embed data
- when you send the document to a friend the document on your hard disk would contain from whom you got the file (email adress) and where it was downloaded
- integrates in modern concepts of organizing the content on your hard disk with desktop search engines like google desktop, ms desktop search, spotlight or beagle. All of them extracting metadata of files to bring them in some context so you can find them easily.