From my own personal experience, I have only had two defective products out of the box. The first was a floppy drive (which I didn't feel was worth the cost of shipping back to NewEgg for an RMA) and the second was a PSU from Corsair that had a faulty +5V rail. I RMA'ed an XFX motherboard, but only after I discovered that I had inadvertently underpowered it with a 450W PSU, so I don't count that one as being attributable to being defective out of the box. I realize that some products can arrive DOA, but I have to wonder if they really left the manufacturer that way or if they became that way due to being mishandled during shipping (yes, accidents do happen!). After reading reviews of various products on NewEgg and Amazon, I also have to wonder if the product might have been inadvertently damaged by the consumers themselves as they may not be taking enough precautions or doing enough research before attempting to install the product(s) themselves. This is particularly true of SSDs! I hear people complaining that they have issues with these devices when they try to bring their laptop or desktop systems out of sleep mode (this is due to the way certain motherboards and their BIOS revisions implement sleep mode), or they have issues with the drive dying or failing on them within a matter of days, weeks, or months after purchasing and installing them (possibly due to cheap power supplies or overclocking), etc.
Despite the possibilities mentioned above, I firmly believe that every manufacturer can and will ship the occasional lemon, or they will manage to produce a specific product (think IBM Deskstar hard drives in 2000-2001) that winds up being a spectacular failure with the consumer. Hell, Intel has made their fair share of technological flops in the past decade of so by attempting to support RDRAM or introducing the BTX formfactor concept to consumers. Most modern motherboards, videocards, and other computer components have also become more complex and demanding in their power requirements with little (or no) room for error than those that were manufactured a decade ago, so combining them with a so-called "bargain" power supply unit may also account for a product being DOA. There are just so many factors to consider that it's difficult to attribute the increase in RMAs to technology alone.