The Copyright Act of 1790 granted the originator of a text "the sole liberty of printing, reprinting, publishing and vending" of a work. Note that it does not talk about mere duplication. Printing and reprinting were at the time very costy operations, produced works of good quality, and required a non-negligible amount of money to perform. On the other hand, if a person was to copy the work by hand, it would not have fallen under this law.
Furthermore, it makes sense that now that we have the Internet that can "copy arbitrary blobs of data from one place to another at virtually no cost, in virutally no time, with virtually no control" (to quote Cory Doctorow), then the copyright laws will once again be ammended to reflect the new technological reality.
Trying to stop such copyright "infringement" on the Internet is not going to be successful. And so far, it seems the Internet helps the originators of such works, more than it harms them.