Where you go wrong though is drawing the parallel between authors making their failed works available online freely to gain exposure (which might lead to future sales being better) and people making the work of others which is still available commercially available without prior consent (and sometimes benefitting financially from doing so).
You're comparing giving freely of your own things with selling (or giving away) stolen goods and concluding they're pretty much the same thing, when they're clearly not.
I don't argue about the POTENTIAL for higher sales due to filesharing technology, but the current practice is that it caused a sharp drop in sales of music CDs and movies over the past few years while at the same time the sales of blank CDs has risen sharply.
Software piracy has now risen to such excessive amounts that companies are sometimes spending more money on preventing it and prosecuting the guilty parties than on the development of the software itself. If they don't, they're forced out of business and if they do product development suffers.
This is not as much an issue in the US as it is in Europe and especially Asia where (at least in the games market) in some countries over 90% is pirated.
The situation in the music industry isn't (yet) as bleak, with piracy accounting for maybe 30% of the market (and some people indeed buying more because they hear a few tracks of low quality reproductions and wanting the real thing, but many people now rip entire albums at near the original quality which are made available and CDs burned from it all over the world).
In stores, the sad result is racks of CDs for sale the boxes and booklets of which have been stolen by people who have burned the CD after downloading it via filesharing. That never happened on such a large scale in software, but might start happening now that software too is being ever more distributed in smaller boxes.
You say the artists should decide whether to make (some of) their work available over the internet and I agree.
But it's the artists who should make that decision, NOT the end users!