Digital first-sale rights

This article on the resale of an iTues song is interesting in it's own right but this paragraph really caught my attention:

"Under the "first sale" doctrine, the owner of a lawful copy of a work is allowed to sell it without the permission of the copyright owner. But a recent study of the first sale doctrine from the U.S. Copyright Office suggested that the doctrine does not apply to digital goods, because such transfers imply making a copy of the work--something that's not explicitly addressed in the doctrine."