Free book give-aways, IMO, are much more likely to lessen obscurity than a file name buried in a multi-megabyte torrent of "1000s of authours i pirated for the lulz" (we're talking new authours here, not "not available as e-book, backlist, or out of print established authours).
If someone is downloading a 1000 book torrent, they are probably doing it to get the couple of books they already know about - the rest of the books come along for the ride and languish on the downloader's hard drive until Mr/Ms Pirate decides to read a thousand books! How long does it take to get to our Unknown Authour? Months? Years? More likely, the unwanted files are deleted as dross unless Mr/Ms Pirate is a file hoarder.
In the unlikely event that Mr/Ms Pirate is targeting our Unknown Authour's book, how did he/she hear about it? Right! Word of mouth, blog entries, Mobile Read, etc. In which case, Unknown Authour is no longer Unknown Authour, but now Semifamous Pirated Authour! Promotion, not piracy, lessens obscurity.
Give me free books, cause I'm a greedy bastard and the first thing I type into that search box is the word "free". I promise that if I like it, I'll buy others. Give large samples - large enough to hook me, cause three pages, most of which are a dedication to your cat, aren't going to cut it. Tell me about yourself on your authour's page, make yourself more human to me (or, in the case of SF authours, more alien

). But you must also promote! Tell the world about your book and why the should read it. Get on review sites, advertise on MR. Tell us you're there, or your only sale will be to your mother.