In order for the last generation of product to become undesirable, it has to break down. Planned obsolescence is the system in which the product is designed, either by mechanism or negligence, to actually become less functional. The next product is marketed with better, more advanced features (Which is usually true) and the consumer is offered no choice when their earlier model is an incompetent comparison.
One of the industries most guilty of this is the tech business. Silicon Valley has done well to smash the Baby Boomer motto of "Built to Last". Our phones barely last a year, just in time for the next generation (I'm looking at you, Apple). This practice is extremely wasteful, and frankly crooked. A consumer should be able to expect quality when paying for a $200-$500 device, but that isn't what they are getting. The industry of innovation and advancement is ethically lacking in this sense.
What can we do about this? We can make a point to boycott those companies that produce short lived products (Ahem, Apple). This is difficult, of course, and can be more expensive, but the long term cost of one durable device versus multiple cheap ones is almost always lower. Changes to be less wasteful and more respectful to the customer are really needed, and by speaking out and making smart purchases we can pull that change closer.