This is hardly a new thing. Gamers in particular have been up in arms about it since the coming of Steam.
Personally I don't have a problem with it, I've never bought any physical or virtual good with the intent of re-selling it (except a car, which I'll get to later).
The reason people take issue is that in the past, when you could only buy games/books/music in a physical format, there was no impediment to selling it to someone else when you were done with it. Most digital goods that are sold today have some way to tie the product to the person who bought it though, usually via a user account of some kind. So people see this as an infringement of their rights because they can't do what they used to be able to do.
In my mind though, the re-sale of many of those goods never really should have been allowed (I wouldn't go so far as to suggest it should have been illegal, but it was never 'right'). Take a video game for example. When you buy the game, you aren't paying for the physical media on the disc - yes thats part of the cost, but what you are actually buying is the experience of playing the game, and the work put in by the developers to create that experience. You paid $60 for that experience and the developer got some money for it. When you turn around and sell that to a friend, the developer doesn't get any more money. You can argue that this is fair because you own the physical media that the game is on and you have certain rights to do what you wish with things you own, but the reality is that they didn't sell you a disc with a game on it, they sold you their work, at an agreed upon price, and you already consumed it. Nobody else should have the right to consume that developers work off of your physical media without also paying the developer for it. This is an unpopular opinion among gamers, but its what I believe to be true and fair. The same idea applies pretty well to books and music as well.
The most common argument I see put forth by people who disagree with the idea that you don't actually own a digital product you buy is the comparison to other goods that are commonly bought, used, and then sold to someone else - cars are frequently referenced. A CD and a car are both physical products, but they should not be treated the same. When you buy a new car from a dealership, what they have sold is a vehicle that is expected to function properly for X number of years/miles. They have no stake in who actually gets the value out of the car, as it can only be used by one person at a time, and if the person who actually paid for it never uses it (because they give it to a family member for instance) they lose nothing - they sold a vehicle that has a finite amount of usage, and the value is consumed as the car is used, regardless of who is using it. A car cannot be fully consumed, re-sold and fully consumed again, then re-sold and fully consumed a third time the way that a video game can.
To provide a simplistic example, lets assume that a car is bought new from a dealership with the expectation that it will run for 15 years. When you sell that car after using it for 5 years, the person who buys it is not getting a brand new car with a life expectancy of 15 years, they are getting a used car with a life expectancy of 10 years. The dealership doesn't lose anything because they already made their money with the expectation that the car would last 15 years - the fact that someone else other than the original buyer is using up that value does not affect them. Compare this to a video game, where the original buyer pays $60 for the ability to play the game to its completion. Once that person is done with the game, he's already consumed all $60 worth of value. When he sells that to another person, that person is also going to consume $60 worth of value, because hes getting the exact same thing that the original buyer got. This can be repeated endlessly, with only a single person buying the game, but everyone else getting the entire value out of it, and not a single cent going back to the developer despite only being paid once. If you take this all the way out to point of absurdity, a single copy of the game could make its way around to every single person in the world, with every single one of them getting the full value out of the game and none of them paying the developer. This cannot happen with a car (and most other physical goods in the world for that matter).