What do you mean exactly?
Discussion
All of your data is public here. All the connections between apps you use are public. You basically create a complete profile of your online activity for the megacorp. And if it’s tied to a real identity - as many are and will be, you’re creating the perfect ad serving profile for anyone who wishes to use it.
Ad serving profiles only work if you use platforms that can serve ads.
The federation of Nostr between relays creates that mega platform
But I won't use a client that serves me ads.