Busted how though? It's not like McDonalds, for example, would use a Mc-branded account to post random things to reddit with clearly visible McDonald cups or whatever. They'd use some throwaway account or buy an established account and buy upvotes to target that account's post. Reddit has no way to punish them for that. Maybe the reddit users find out and get pissed, but the site has no attention span and they'll forget and move on in a week.

I get your point but do you think that massive brands like McDonalds would take this path to show you a hidden ads about their brand. no. They can pay millions to blast you their McDonalds cups on TV ads. When these kind of companies want to start to put ads on a new media they have 6 or 7 figures budget. They don't give a damn about paying a 100USD gig to have their McDonalds cups's post on the front page for 3 hours. They want their McDonalds cups on the front page ALL the time.

Why wouldn't they though? Astroturfing gets around adblockers entirely and reaches those who are ad-adverse because they don't necessarily realize it's an ad. It's nothing new either, it's just the internet equivalent of sitcoms having name brand products visible (and "coincidentally" turned turned so the logo faces the camera) during the show or "I, Robot" having "retro" chucks featured prominently (although obviously way more subtle than that).

My assumption is that McDonalds pays advertising companies to put ads together and distribute them. Why wouldn't they throw a couple hundred bucks at a few low-key ads in a few reddit posts. Doesn't take that many people to buy McDonalds before it pays for itself.

Also, everybody does it. Every major brand already has many thousands of followers with questionable names in clearly irrelevant locations, and this on a platform where such shenanigans are visible to everyone.

There's no reason to believe upvotes, which are less visible to other users, are bought at lesser scale.

When everybody does it, it's hard to single out any one actor as bad.