That would be horrible if you had other systems that predated and did depend on the null (you could argue they shouldn't do that but well shouldn't and didn't aren't the same thing alas).
Why is NULL a bad thing? Sometimes I absolutely want to know if a field is NULL, so i can coalesce to the desired value. I know this is SQL Server specific, since Oracle treats empty strings and NULLs the same, but that approach has always felt wrong to me. Thoughts?
Edit: I see maybe that I should have scrolled down further before posting this. Lots of discussion further down about NULL values.
Using UUIDs as a primary key is considered an anti-pattern from space and performance standpoints.
You should use UUIDs only when, you know, you need a UUID.