Dire Bare
Legend
Once the phone is jailbroken, both legal unofficial apps and illegal pirated apps are as easy to use as any program on any computer (generally easier, actually, because mobile software lacks the overengineered DRM schemes that pollute so much desktop software). At this point it's just a matter of sharing files online, which, as you say, "is pretty cake."
Also, how difficult a thing is to do (jailbreak a phone) versus how difficult a thing is perceived to be, is important. Techies might know that pirating an app is marginally more difficult than pirating an MP3 song or PDF gamebook, but for non-techies (like me), the perceived difficulty or risks may make it less likely they will do so. I totally believe your explanation above, but I am still unlikely to try and jailbreak my own smartphone.
I "know" that downloading pirated MP3 songs, movies, or PDF files could potentially end with a lawsuit against me, as it is common knowledge that the RIAA and MPAA have been aggressively litigious in the past, and that the publishing industry is showing signs of moving that direction as well. But the practice is so easy, and has been for over a decade (if not longer), and add to that the common human fallacy of "it won't happen to me" . . . a lot of folks share media files without much of a second thought. (although I'm sure the average joe is still uncomfortable enough with "torrents" and the like to not bother going there).
But if I jailbreak my phone, I void my warranty if Apple (or whatever manufacturer) finds out, and it's common experience that these things break all the time. I think that most people fear that any type of computer is one coffee spill or random electron discharge away from malfunction. So even if jailbreaking is easy, I doubt most folks would consider doing it, and certianly less folks than would consider downloading a pirated song or book. That might not actually model reality all that well, as I'm sure my techie friends could point out, but the perception of it not being worth the risk is there. I'm sure over time, jailbreaking a mobile computing device will be seen as just as common, just as easy, and just as relatively harmless as downloading iffy media files, but I don't think we are there yet.