one reason the file name is hidden is that it's obvious where the uploads directory is in both threads and vb. Knowing the name of the attachment will allow someone not logged in to download any attachment because they would know the name of the file. The way threads handles it keeps your attachments only for logged in users should you choose to protect them like they do here
IP numbers aren't meanlingless to most people who run forums.
The way attachments are handled is a personal opinion, but I like the way they are done here
