I propose using a single sequence for the bigint identity columns of most or all tables. (Essentially, OID, except 64-bit.)
This helps prevent security problems for a multi-tenant application that joins tables incorrectly.
While a uuid could be used for this, bigint is half that size, helping save index space.
My understanding is that sequence generation is very fast in PostgreSQL.
The only downside I can see is widening the type of tables could get by with 4 byte integer IDs, but thanks to PostgreSQL upsert behavior (generating a new value whether or not it's needed), I rarely use int IDs anyway.
Is there an issue with approach? I haven't found anyone advocating for it, but I consider the join safeguard to be quite nice.