You're right. More specifically, programmers have argued that complex schemes involving encryption and similar technologies will protect them in court[1] from lawsuits. The essay "What Colour are your bits?" at http://ansuz.sooke.bc.ca/entry/23 explains in detail why this won't work.
1: as opposed to keeping people out of court in the first place, which crypto technologies can plausibly do.
My point isn't that "it's just a little piece". Like being "a little bit pregnant", I don't think that "infringing a little bit" could amount to much of an argument.
It's that with certain methods of encoding, a piece is entirely worthless without the rest of the file. That is, I could give a chunk to the IP owner to inspect, and there's no way that he could tell me if it represented a part of his work.
if a certain ordering of bits makes up the left breast of a child if interpreted as part of a Jpeg is that illegal if randomly occurs within...
This makes me think of the Judas Priest "back masking" trial way back when [1]. The wikipedia article notes "The case was dismissed by the judge for insufficient evidence of Judas Priest's placement of subliminal messages on the record", and that's a little ambiguous: do we read that to refer to the existence of the message, or to the intent to put the message on the record?
Anyway, for the danger that you outline, I would think that if it's possible to transform a data stream into a different context in which it could be construed as illegal, then the evidence would also need to include possession of, or access to, a means of accomplishing that transform.
Without some kind of consideration of this, steganography would throw a wrench into everything.
Surely, even without encoding, the piece is pretty worthless without the remainder of the file.
But I see what you mean though (you couldn't even reconstruct a portion of the file).
Im not sure it matters; the point is definitely the intent to supply the copyrighted media in whatever form. It's similar to the persons idea not long ago of supplying obfuscated MP3's by encoding them as Tweets and then supplying the code or algorithm to recover and reconstruct the file. It's all part and parcel of the same thing. It's just obfuscating the delivery method not the actual package/intent.
More importantly I don't think the court will be sympathetic to the idea; and if that is the case it risks invalidating other arguments you may bring.
(there is a similar thing in money laundering; many launderers try and get away with it by rotating very small parcels of money from lots of different batches through legitimate transfers. The idea is twofold; it's difficult to reconstruct the original larger packets of illegal money and b) they can claim, for various reasons, they had no idea of the origin of the money. This argument, as you can imagine, doesn't last long in court :))
I think, ultimately, it is not currently possible to fight the idea that distributing copyright materials in any form could be legal (or at least not illegal).
My response is usually: "were you uploading copyrighted stuff?". Answer: "yes". Me: "well then..."
Saying "but I only gave him a small piece of data - what he does with it is his own business" doesn't stand up because clearly your intent was to give him part of the file so he could construct the file (this argument has been used for centuries to try and get out of things and almost always fails :P)
Seriously? I think people should just suck it up, admit they did something wrong (currently wrong anyway...) and then fight the idiotic fine.
Ultimately the law is not really about the exact bits you exchange (one of the few things I agree with, actually) but about your intent and facilitation of the shared file.
EDIT: to clarify/extend something. I think it is a dangerous road to bring the idea of what the individual bits you send mean - because that starts to open up the idea the a certain ordering of bits could be illegal (take a CP case - if a certain ordering of bits makes up the left breast of a child if interpreted as part of a Jpeg is that illegal if randomly occurs within a music file you own. Or perhaps the bits in an MP3 appear by random occurrence in a video file you own. This is a dangerous weapon to hand people :P)