Why social network providers? No.  They only point your long npub to a human readable addresses. Of course they can remove you. It's their domain. Just like email providers can refuse to keep your email accessable. You can buy your own domain and set the nip05 for your own name you want,  like I did for example. Bought a domain and that's it. But if we go further, yes even domains can be taken away from us unfortunately. There are not many things in our modern lives we truly own. But I know for sure, Bitcoin private key and Nostr private key are one of them