At TPAC there was some concern about limiting publishers to a certain number of issuers (notes). This was a trade-off that we made between utility and privacy, because the more issuers there are on a page, the more bits of user-identity it is possible to leak in the worst case.

@tomlowenthal mentioned there might be an approach that can put a ceiling on the cross-site entropy by having some degree of negotiation between browsers and sites, and to allow browsers to pick which issuers to use (and do things intentionally inconsistently). Tom can you elaborate on what you were thinking here?