I would agree. If you run a free hosting provider, try promoting yourself on forums about free hosting as well as try getting into the top lists and free hosting directories of any kind. Most of them will require a backlink, but that's part of the business.
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You could always try hitting up "file hosts" and see what advertising they have available? Most of these hosts (file hosts) allow users to host for free so turn up a google search and see where they are located.