git-annex has multiple key-value [[backends]]. So far you have been using
the default, WORM (Write Once, Read Many) backend.

Another handy backend is the URL backend, which can fetch file's content
from remote URLs. Here's how to set up some files in your repository
that use this backend:

	# git annex fromkey --key=URL--http://www.archive.org/somefile somefile
	fromkey somefile ok
	# git commit -m "added a file from the Internet Archive"

Now you if you ask git-annex to get that file, it will download it, 
and cache it locally.

	# git annex get somefile
	get somefile (downloading)
	#########################################################################100.0%
	ok

You can always drop files downloaded by the URL backend. It is assumed
that the URL is stable; no local backup is kept.

	# git annex drop somefile
	drop somefile (ok)