The first association that leaps to mind when someone mentions youtube is probably not Marx. In fact, he is probably not among the top five or the top fifty. Which is understandable, given that Marx is something of an 1850s guy and youtube is not very 1850s at all. The line between these things is not altogether clear.
Unless, of course, you are a David Harvey fan, and have listened to his series of youtube lectures on the man.
Those who have dabbled in creating youtube videos know that it is difficult to predict just how many viewers a video will get. There tends to be an average number, and some variations up and down for the most part. Then, seemingly for no reason, there are videos that get far more viewers than the others. Seen in context, they are the same as the other videos, except that something funneled viewers into that one video in particular. With enough sifting through the stats, it is sometimes possible to figure out what's up; if you do, then that is useful information.
Anecdotal evidence has it that it is usually the videos that took the least effort to make that wins this accidental lottery. Conversely, those videos which take hours upon hours to produce tend to remain at their usual levels of viewers - possibly slightly fewer, just out some spiteful statistical quirk. This perceived inverse relationship between effort and outcome is probably just imaginary, but it's easy to feel that it would be better if viewers flocked to the effort-intense video rather than to the throwaway two minute thingamabob. If viewers are only gonna see the one video, then it might as well be one of the good ones.
As it happens, Marx has something to say on the matter of the relation between effort and results. Specifically, he talks about socially necessary labor time. It is a very technical concept, given that you have to understand what "socially", "necessary", "labor" and "time" are defined as in order to really get the full story. The short of it is thus: if it takes you five hours to make a pair of shoes, and your competitor can crank out thousands of those same shoes in the same span of time, the market value of the pair you made does not go up because it took you a lot of time and effort. Consequently, any attempt to sell them at a price that corresponds to your time and energy invested will fall flat, given that there are other shoes sold for cheaper.
This has consequences for your career as a shoemaker, as you might imagine.
It also has consequences for all shoemakers. The competitor who put you out of the shoe business has to face the same dynamic. He can crank out shoes by the thousands, but if someone comes along who can produce tens of thousands of shoes in the same span of time, this is going to be an issue. The same dynamic that made it unfeasible to make one pair of shoes at a time, also make it unfeasible to remain someone who merely produces thousands of shoes. The sheer amount of shoes will drive down prices until it becomes an economically sound idea to either upgrade the production line or move into another line of work.
If you are tempted to say that this is why capitalism is good, seeing the immense amount of shoes it produces, Marx would agree with you.
The main point of the concept of socially necessary labor time is to decouple personal effort from market outcomes. As you can see in the example of shoemaking, the price someone is willing to pay for a pair is not based on personal factors; there is an impersonal dynamic at work beyond any one person's capacity to control. Those who want to compete in the shoe market, have to produce shoes in such a way that it makes sense in terms of price and production capacity. One pair every five hours simply will not cut it, even if you worked really hard at it.
The same goes for youtube videos, in two important ways. The first is most obvious, so let's get at it first: expending vast quantities of time and effort into producing a video does not guarantee that viewers will flock to it. There is always a risk that you are making the youtube equivalent of those five-hour shoes, and it does not reflect badly upon you if this turns out to be the case. It's in the nature of the game.
Less obvious, but equally as important, is what this tells us about those who crank out videos at an alarming rate without investing too heavily into the research or production quality departments. It is easy to become resentful and mutter about the unfairness of it all, where hard work is left unrewarded in favor of these clowns. This is not a useful state of mind, however, nor is it a useful analysis. Instead, it makes more sense to see it as an instance of socially necessary labor time: apparently, this is how many videos you have to crank out in order to remain competitive, even if these videos end up containing easily preventable errors and mistakes.
If you are tempted to say that this is why capitalism is bad, seeing the immense amount of shoddy videos it produces, Marx would anachronistically agree
To reiterate: the point here is to decouple effort and market outcomes. Working hard in the sweat of your brow is not a reward in itself, nor does it guarantee that viewers will show up. Finding ways to streamline your process and make time for other things (or to do things better) is not cheating, it's just efficient. Moreover, being hard at work does not mean viewers owe you anything; being resentful that they are not appreciative enough of your efforts will not help you going forward. Conversely, if it turns out viewers really like that throwaway two minute thingamabob, then that is useful information.
Needless to say, if this goes for shoemaking and making youtube videos, then the notion of socially necessary labor time probably goes for a lot of other things as well.
Marx is sneaky like that.