I haven't heard much discussion about DRM lately. I don't know if that's because it's no longer a popular subject, or because I haven't been paying attention. The only reason I am thinking about it now is due to my recent book. When I uploaded "The Songs of Chaos" I had to choose whether or not to enable DRM protections, and whether or not to allow lending. I answered no, and yes.
I have been watching software, and to a more limited extent media, companies in a panic-stricken scramble to maintain a death-grip on their products for decades. Some of the old methods were plain silly. The very early floppy disks had a little notch along one edge. If the tab was broken off, the disk drive would not copy to that disk. Some companies ran themselves into madness trying to use that fact in various bewildered schemes. None of them worked of course. Duct tape. Grasp the concept.
Then there is the immortal dongle. By any other name, it is just as much of a pain in the ass. (Get your mind out of the gutter. I am not making the name up. The dongle is the old word for a piece of hardware that has to be plugged into a system before a program will run.) Some of the more expensive CAD packages used to be fond of using it. Start the program, and it would check the serial port for the presence of the holy dongle. They quit messing with this kind of bullshit when people quit giving them money, due to the fact that the software packages, which cost a mint, frequently went haywire and refused to recognize the hardware.
Then things got really dumb. I mean Dumb. For instance, I bought a game once, I think it was called Star Control, or something like that. It was a primitive, DOS based game with EGA or VGA graphics that had you controlling a tiny little spaceship in battle against another tiny little spaceship, while trying to avoid bumping into planets the size of grapefruits. In order to start the game (Please note. I do not mean install. This was after you had installed it. I mean EVERY TIME you wanted to play it.) you had to dig out a little cardboard thingie like a secret spy decoder wheel. It consisted of three nested pieces of card stock, with little windows cut in them. The computer would pop up a random code. You had to align the magical decoder wheel and come up with the right answer, then type it into the dialog box before you could play the game you had paid for. When the cardstock got tattered or coffee soaked, your gaming days were over.
The Space Quest series was immensely popular for a while. It was prone to letting you get halfway through the game, then tossing random questions at you from the user manual, like "what is the third word from the end of the second sentence in the fifth paragraph on page 109?" If you couldn't answer the question, you were screwed. Paying customer be damned. So you better not throw away the manual. Of course, there was nothing to stop you from photocopying the the manual, and then breaking out the handy-dandy duct tape to mass produce copies of the disks for all your friends. Shhhh!
Another space game I had came along with one of the computers I bought. I am not sure if it was the 8086, or the 286. It was a First Person POV game where you flew a fighter space craft on escort missions and attack runs. Pretty tame by today's standards, but it was fun. Thing is, you would invariably run low on fuel and ammo, and need to pull into one of the various space stations scattered around for restocking, and also for repairs. In order to get into the station, you had to type in the proper identification for the station you wanted to dock with. They were all listed on the map that came with the game.
You guessed it. We didn't get a map. I had to obtain a hex editor, crack open the executable, and read the ASCI parts of the file in order to extract the names of the stations so I could play the game.
This is all leading up to my point. I don't bother with DRM on my books because I have never seen it accomplish anything except aggravation for a paying customer. Anyone savvy enough to steal a computer file is certainly savvy enough to crack a DRM scheme. And in fact, I am confident that there is already more than one cracking program out there for the kind of books I publish. I don't know for sure, I haven't looked, but I am confident that they are out there. I see no reason to make life difficult for my paying customers, and accomplish nothing in the time of it. Besides, who knows? Today's pirate might be tomorrow's purchaser.