From the comments section of All Content Creators Should Watch Porn - The Illusion of More (don't worry, the article itself is SFW):
... a glut of supply in a time of reduced demand drives prices down – or, in other words, that all producers are worse off in this situation.
It gets even better (worse): the big guys are actually at an advantage here. The sheer amount of music being put out there means that potential customers (fans) have no way of sorting through it all and making an informed decision. At this point, standing out above the crowd becomes paramount and the big players are in a much stronger position to do so, because they have the promotional budgets and media connections. You might argue that this can be offset by “guerilla marketing” tactics, but – frankly – that’s an illusion. Oversupply gets you here too, I’m afraid. Someone who has been spammed to death by legions of hopefuls with no talent simply isn’t going to be receptive to even well-meant attempts at self-promotion by yet another artist they’ve never heard of. At this point, you really need to have a trusted taste-maker plugging you or you will be dismissed as yet another crappy, self-published act, which are legion.
Most of us turn to reliable sources — a person we trust, a taste-making platform, an institution we associate with quality (publishing house, record label, hot-shot director) — when we want to find out what else is out there. Those who have the cash on hand to buy attention always win — not because such an arrangement is corrupt, but simply because there are that many more ways to get people's attention when you have money, then there are when you don't.
I've become skeptical of guerilla marketing as a way to throw a grappling hook over that particular wall. Not because it doesn't work, but because the number of times it does work is vastly dwarfed by the number of times when it doesn't — and because the penalty for failure is far more punishing. If you solicit the conventional way and nothing happens, the worst-case scenario is that you're out a few bucks for postage. If you guerilla-market and do it badly, you end up making yourself into box-office poison with some of the very people who you're supposed to be ingratiating yourself with.
One of the things that gets overlooked with regard to using someone else's promotion mechanism is that the people who do it for a living generally have a far better idea of how to make something known without being jerks about it. But they have good reason to be stingy with the expertise and connections that go with it; those things are power and leverage, and they scarcely want to surrender them to competition.
I self-published because I felt a lot of what I had to offer would only be of interest to a small, self-selecting audience. Now, I'm skeptical: I need to see what else is out there, and the only way to do that is to play someone else's game. Emphasis on the word play: I'm only doing this to see what happens, not because I have my self-esteem banked on the results. That, I suppose, is the most constructive way to think about it. No matter what happens, I'm still a writer, and I still have my work to my name.