1) DRM is bullshit. Essentially, when you purchase a PDF, it SHOULD be like buying a book. If you want to lend it to a friend, you do so. PDFs don't work that way because for some reason, idiots think letting anyone look at something you paid for is somehow affecting their bottom line. Whatever. DRM is supposed to correct this problem by simulating the physical presence of the book or something. One viewer at a time, however you want to look at it. The model breaks down instantly in practice. There is no real way to create a pseudo-physical presence for a book with any sort of copy-protection scheme in the first place, and secondly, all you do is piss off the people who actually paid for the thing. Pirates are going to steal regardless of how you manage your PDFs, and legitimate customers will wonder why they have to type in passwords or see their name plastered all over the book they paid for. The whole "bottom line" reason for implementing DRM is worthless. When a thief steals a book from a bookstore, there is a tangible effect, a real monetary loss. What loss is there when a pirate steals a PDF book? The PDF can be reproduced infinitely and sold to whoever wants to buy it; there suddenly isn't one less copy of the PDF that cannot generate revenue. Further, 99.9% of the time, pirates wouldn't have paid for the PDF in the first place, so there isn't a "lost sale". It's an essentially meaningless feel-good anti-theft device that does nothing but make it harder for customers to get their stuff.
2) Non-persistence. So I buy this book in PDF, and I'm reading it, but then all of the sudden my computer acts funky, now the PDF is corrupted somehow and I have to fix the errors I'm getting trying to open the file. Or I get a new computer and the PDF decides it doesn't like being copied. Perhaps my computer explodes, and like everyone else my extensive tape backup library was lost in a fire. Goodbye PDF. Hey, wait, I know...I'll upload all the PDFs to an online backup so I can look at them whenever I like. Nope, looks like the RIAA is turning the screws on all these companies to prohibit "copyrighted material" on their servers. Well, okay, I have an account on Paizo or RPGNow, hey wait a minute...they went out of business. Adios, PDF. If my collection of D&D books burns up in a fire, I can probably get copies off eBay or at Half-Priced books to replace them. My insurance company will probably reimburse me. PDFs lost into the aether are pretty much done with, EVEN THOUGH the intent is that they can simply be downloaded again. If the company goes out of business, where do you get the PDF? I suppose you could pirate it, but then you have to deal with DRM, for your legit copy that is now non-legit. Yeah, okay.
3) Horrible interface. It's stupid to model electronic information on physical medium because they're inherently different. The whole point of electronic books is that you can have a ton of them with you on your laptop or iPad, but I cannot read them on a computer screen. It just hurts my brain due to the book paradigm I'm used to. Webpages, yes, I can read those just fine, due to the format. But book-type information belongs in a book. Further, I can't take PDFs with me into the john, throw them in a backpack and not worry about damage, leave on my desk and figure no one is going to steal it and take it to a pawnshop. For instant reference type stuff, perhaps a drug guide for doctors or metal fatigue charts for engineers, electronic books make sense. For something I just want to read, it sucks. For me, at least. There's nothing like getting your hands on a new book. A new PDF, well, it's just a PDF.
4) Required buy-in. When I want a PDF, I have to buy it. There's no option to view it first, then purchase it. If I want a book, I might look through the whole thing before spending a dime. Actually, I buy almost all my books through Amazon, so I may not even look at them prior to spending money. But if it sucks, I can probably sell it to someone else, maybe put it on eBay. Can I resell a PDF? Uhhh, no. Stuck with it. And what happens if you mistakenly buy two copies? You got suckered. A real book, I have two copies. Maybe I'll give one to a friend. With PDFs, if I give a friend a copy, now I'm a pirate. Considering I could make 1000000 copies of that same PDF, I essentially just wasted my money. Two true examples: accidentally purchased two copies of the new BRP from Chaosium's online store. Great game, by the way. So I email them about it. No response. Tried for three weeks. Finally I contacted AMEX and got a refund. If I had purchased two physical copies by accident, return one, no harm no foul. Or, hell, just keep it and give it to someone else. Same thing happened with Swords & Wizardry Complete as mentioned above. Got the Pazio PDF, sucked because of watermarks. Then I bought the physical copy which came with a PDF. So, yeah, $10 down the toilet.
5) Overpriced. PDFs cost too much vs. physical books. Seriously. When I bought HERO 6th edition, they gave me copies of the PDFs for free. I could buy the books for $60, or the PDFs for $50. WTF? $50 for electronic copies that are only $10 less than the physical books? Books that weigh literally five pounds, full color, hardcover. NICE books. Where's the incentive to get the PDF? Seriously overpriced as hell, if you ask me. For $5, I'd buy every single HERO PDF they publish. But they seriously want almost as much as the physical books, which means I just order the books from Amazon. Screw that.
I don't advocate stealing anything, especially PDFs. But I'll never pay for a PDF of a book I already own in hard copy. Ever. I downloaded some scans of Chivalry & Sorcery. Illegal, I dunno. I don't care. I have three boxed sets of that game (it was four, but I gave one to Chris: you're welcome), why would I want to spend $20 or more on electronic copies for something I already own three times over? I could scan them in myself if I wanted and it'd be Fair Use according to the law. So why is getting a scan from someone else suddenly piracy?
Comments are especially welcome.
ADDENDUM: I remember hearing about Eclipse Phase, thought it sounded cool. They offer the PDF as a free download that you pay for if you like it. Downloaded it, decided it was great, bought the physical book. Why don't more companies do this?