Notably, this started happening the day that I made my TikTok account public. My Instagram feed began to be a copy of my TikTok feed. The exact same videos. Even after changing my Tiktok back to private and deleting all of my followers, the feeds are still identical, every single day. My behavior is not. On Instagram, I follow and interact with very different accounts than on TikTok. It seems to me that Instagram is buying or accessing TikTok's data, and it is not through advertising providers, because the identical content is coming directly from Instagram/TikTok and not promoted ads.

They don't have to collude, the third party advertisers that collate and provide shadow profiles do that work for them.

Not sure if they're explicitly sharing data, but there does seem to be something that's sharing data across the platforms. When I buy something from Tiktok, the ads for the same thing shows up on my instagram almost instantly. Doesn't necessarily mean they're directly sharing data of course, could be a third party too. But as a consumer that has very little difference for me.

Not so laughable after working in big tech