1) Yog's Law presupposes that everyone will, or at least should, be doing their job. This is ceasing to be the case at landslide speed. For instance, publishers used to do a substantial amount of publicity that used to be more widely (though never evenly) spread among their authors. Now a book might get nothing more than an entry in the publisher's catalog and a page on Amazon. Various other things that a publisher, agent, or other party used to do may also fall out of practice in some instances.
Well, not all authors are content with this shrinking service, and some of them have both the determination and the money to do something about it. They either do it themselves, or hire it done, or frequently some combination of both. This means that a prudent author, who wishes their work to reach an audience effectively, will keep an eye on anyone handling said work to make sure that necessary jobs do, in fact, get done adequately. And if not, the author should consider whether it is feasible to pick up the slack in case of letdowns.
2) The publishing bottleneck is breaking up. More authors (and readers!) are turning to alternatives such as micropresses, self-publishing, crowdfunding, etc. So instead of a Big Name Publisher with hundreds of employees to do (hopefully) all the large and small tasks of putting a book into print -- we have tiny teams of a few people, or individuals, trying to produce the same end results. Therefore, the supply and demand for freelance services is rising. Popular services include proofreading, editing, cover art or other illustration, layout/design, printing, promotion, webcoding, and so forth.
A writer, or a writer and the owner of a micropress, will typically look at the available skill set and compare that to the needs of a given project. There is often at least one gap. So, a freelancer will be hired to take care of that task for that project. Next time, somebody else might be hired, or the project head might have developed that particular skill. Or the next project could have a different gap. Instead of a semi-permanent employee pool at a publishing house, there is a much wider pool of people who know (or know of) each other and their various skills, joining and parting based on the needs of the project of the moment. They may work for cash, or decide to trade skill-for-skill ("I'll write some content for your new art portfolio website in exchange for a cover picture of my new manuscript."), or some combination.
I think that Yog's Law makes sense in regards to the publishing world it was originally meant to cover. But writers are no longer stuck with that as their only option, and outside of it, other approaches may work better. How to determine the appropriate direction, then? In general, if someone demands money from you, that's a bad sign. If all you do is write, then money should indeed flow toward you. If you decide that you want to buy something or hire someone, that's different -- just make sure that when you spend money, you do so prudently. Do you research ahead of time, including at least a rough cost-benefit analysis. Make sure you know what you're getting in exchange for your money or barterworth. If a publisher shortchanges you on services, that's a bad sign; you might consider dealing with somebody else next time. If you decide that assembling your own project via freelancers is a more efficient or effective business model ... well, then, you've basically declared yourself a micropress, so go for it. Do your homework. The risk is real, but so is the chance of reward.