For me personally it's not a problem that OpenAI can scrape my posts, it's a problem that only OpenAI can scrape my posts.

I don't want one company to have the monopoly to train an AI on everything that me and all my friends post on a particular platform. If we're going to decide that training AIs on scraped data is fine, then everyone should have equal access to the dataset. Otherwise it's just a massive data grab and a massive transfer of power to whoever wins this data race, enacted by some platform owners hoping to monetize their users even more