It's really making buying decisions based on other people's opinions, at its heart. Essentially buying based on perceived value of tier or creator - so for instance I'm into tobacco pipes, and at thee low end you have whatever factory pipes, then you have a mid range, then you have a high end. I've got pipes across all of those. And of course there's the tobacco you smoke.
I see a ton of crap in the mid-level range because it can sell. People moving from factory pipes to "artisan" pipes for the first time, buying fat turds solely because it was made by an individual rather than a factory, because it kinda sorta looks like a pipe that another more skilled carver pulled off well. Enough so that folks who literally haven't seen enough to know what they're even looking at and go "hey that's pretty good and I didn't even get suckered by an even higher cost".
Then you see people collect tobacco before even knowing what kind they like. Latakia is heavy and smoky, Virginia can be haylike and grassy. There are ranges on each end of the spectrum as well. There are rare tobaccos on each end of the spectrum. Just because it is hard to find and expensive, does not mean that you will even remotely enjoy it. But people still stock up, because it's impressive to others, and because surely they'll figure it out, it's rare and expensive, it has to be good.
I feel like bonsai can be the same, which is why a new person can look at a mallsai and see an ancient juniper. They just haven't seen enough to even know what they're looking at, even if all the academic pieces are in place. Typically it's around aesthetics and personal opinion, I think that's why say nouveau riche in stories have the stereotype of being gaudy, they haven't been buying art long enough to know what their taste is.
Beyond all that, other newbie pitfalls:
#1 - Buying way too much way to early, and most of it bad. As others say, the foundation you're building from is what you rest everything upon. 100 bad things does not make 1 good thing.
#2 - Focus on acquisition rather than enjoyment - there's always going to be someone with a bigger hoard, a more impressive something, a more rare something. Don't chase it. It's not a sign of enjoyment or quality.
#3 - Spend too much time on forums - I'm guilty of this because I bore easily and it can feel active, like I'm doing something. Forums can really change your perception, and your taste will be influenced by it. Your sense of what's normal changes, because you're surrounded by people as into this thing or more into this thing as you are. This usually results in thinking #1 and #2 are a normal part of the hobby, because the folks in #2 are the ones sticking around posting the most and influencing the tone of the forum. The hobby isn't "consumption", the hobby is "bonsai".
#4 - really, ultimately, just never progressing beyond #1 because you get firmed up believing everyone else is a lunatic and you're the one who finally broke the code. This is usually where I see people posting hero shots of a pile of a billion of some mediocre thing. You don't need a pile of a mediocre thing, and it quickly adds up to a lesser number of very high quality things if you are determined to spend the money.
#5 - think about what you're going to use and enjoy. Don't turn it into a job. I think with bonsai this is really tough with all the cuttings and such, it adds up quickly. I'm not running an actual nursery. There is a limit to the amount of pipe tobacco I can smoke in one lifetime, well aged or not. Again, this level is different for everyone.
That's what I can think of off the top of my head.
