Jennifer, I don't have any major disagreements with you, but wanted to counter a couple points, even so.
Jennifer R P said:
1. People who have some kind of moral objection to paying for stuff. I actually once knew somebody who thought copyright should be abolished and who said that copying a book was "as much work" as writing one. I told her to try it then. You'll never make a sale to these people.
I know people who think this way, too. That doesn't make their rationalizations correct, though. Often, such folks work a day job, so I simply ask them to start volunteering 100 percent of their time, rather than accepting a paycheck. It's hard to counter that and still sound sane and rational. (Though some don't care about that, either.)
Jennifer R P said:
2. People who can't afford to buy anything right now. And before you say "But it's a $2.99 ebook" I *personally* know people so poor they scrounge food from dumpsters. If somebody can't afford food, they can't afford an ebook. These people may turn into paying customers when their circumstances improve. Libraries are the only thing that reduces this kind of piracy.
On one level, yes, I understand this.
On another level, if they can afford to acquire a PC and/or a Kindle in order to read eBooks to begin with, they obviously have SOME resources.
There are plenty of "legit-ly" free eBooks available, so there's not a lot of reason to pirate books that are not. Maybe they don't like the much-higher prices (generally speaking) of trad-pubbed authors... maybe they're currently broke because they're in between paychecks or jobs or whatever... but with all the legit free books out there, again, they could just wait.
Being unable to pay TODAY is not a legit rationale for stealing content TODAY. We don't have to be an "immediate gratification only" society.
Jennifer R P said:
3. People who want a free sample - which is why providing a few things for free is a good idea. I always make sure there's stuff linked to my website readers don't have to pay for. Free samples are good, but in electronic goods, if you don't provide them people will steal them.
Again, understandable... but there's a huge difference between a SAMPLE and an entire work.
Even big authors often offer free samples of significant length. I don't think there's many books James Patterson has published in the last three years where he didn't have a "The first 20 chapters FREE" sort of release out there... and his books are "spendy trad-pub" titles.
So I don't agree with this category as a legit excuse for piracy. There's way too many ways out there to get free samples without resorting to piracy.
Jennifer R P said:
4. People who just want a DRM-free copy.
Which is part of why I don't use DRM.

You gotta pick your battles, and even I don't like DRM, so I never use it. My feeling is, I'll pay once for something. Not once per device. Just once.
I generally agree with your breakdown on types. I think 3 & 4 are easily satisfied... most every eBook site I know provides a free sample automatically, and some authors provide longer free samples by their own choice, as in the Patterson example.
Category 2 needs to exercise some patience... If they own a Kindle, they have some resources. There's plenty of legit free stuff out there, so buy the free stuff that's out there on Amazon, and hold off on the paid stuff when you have some money. It's a pretty sad excuse for piracy.
And category 1 is completely self-serving, the sort of "committed pirates" who will embrace any sort of rationalization that makes them not feel like the "book thieves" their actions reveal them to be.
I don't think that category is huge, though. I know they're out there. I'm not gonna try to fix 'em. But they should know that if they end up as the next Jammie Thomas-Rasset, it'll be hard for me to weep for them....
I mean, it's one thing to say "I can't afford a book I really want right now."
It's another thing to say, "Authors are *expletives* because they're all rich *expletives* and I have a moral right to own whatever they produce simply because I want it. It's wrong for them to want to be paid for their labor."
Yes, there's no curing that, any more than there's a way to cure those who go on Discovery Channel's pot-growers show and say, "Yeah, what we're doing is against the law, but it's a B.S. law, so yeah, I'm breaking federal law (not Washington state law or Colorado state law) on national television. So what? I dare the feds to arrest me!"
There's no curing that. But it doesn't make the behavior right or legitimate, either.
I mean, what if someone committed a murder and said, "Hey, I have a moral problem with the laws against murder. Some people NEED killing, and all I did was act on that, which is my sincere belief."
Yeah, but that person will still be charged with murder...

I'm far more libertarian-minded than statist, but that doesn't mean we all get to decide for ourselves what's legal and what's not...
P.S. Someone above stated that people "only" read a book 1-2 times. I'm not at all in favor of the idea that one should limit how many times a book can be READ. That's worse than even the most restrictive DRM stuff out there! If I've paid for a book, and it becomes a favorite book, I should be free to read it as many times as I want... whether someone thinks "people never re-read favorite books" or not!