There's been a influx of "memes" that just say things like "when you buy new sunglasses from x.com" and it's just a picture of Leonardo DiCaprio making a face. My own friends repost these things on social media because they are "funny". Not only do people not see problem, they literally see ads as worthy of being reshared.

Yes, companies on Reddit have learned to use memes to promote their product organically on that site. And if a meme is particularly good, soon you have unaffiliated users happily parroting it, just like that "Hotel? T***" which I've seen mentioned so many times on that site from random users.

Or just have a memelord managing your Twitter, and soon your latest funny post will find its place all over the internet. I have never eaten at Wendy's in my life nor stepped on US soil once, yet I have seen their "memes" dozens of times.

They don't, honestly this stuff goes to the top and its been this way for a long long time. Any niche interest subreddit that has gear or products has a sidebar with some stuff that's ordained by the moderation team to be "The best X for Y" and therefore incessantly recommended in the comments and all over the subreddit. Sometimes you will even see metathreads where the users are complaining about the recommendations listed in the subreddit's official wiki or faq page.