A small addendum to what I previously wrote: You can already see this in practice.
I was just scrolling through the list, which is now populated by other Threads accounts as well, and I found this account, that I won't tag here (for people on Mastodon, see pic 1). It already tops place 134 as the most followed account in the Fediverse, as of writing.
This person publicly claims that is an Amazon Associate and that is posting affiliate links from which is earning money from qualifying purchases - and as expected, the profile is full of these links (see picture 2 if on Mastodon).
Now, one might say, "but what's wrong with this? People might be interested in getting deals on stuff they want" - and this is true, I do not think what this person posts is simply useless or toxic to everyone. But the fact that it's so high up in the top of the most followed Fediverse profiles gets me worried. Many people do see stuff like this as spam, and would rather not see that in their feed.
And if that person is also paying to get higher up in the feeds of Threads users, specially those that are not following the guy, that is spam, and it's not the appropriate behavior.
This is just illustrative of the state of Threads, another #Meta product, next to #Facebook and #Instagram, and why any self-hostable, open source Fediverse platform is still a better choice to the Fediverse overall, than it. It is also concerning if more such profiles are topping the most followed Fediverse profiles and destroying its quality overall.