inherited SPF record

Meng Weng Mong wrote:

> perhaps when the game has progressed a little further we can
> solve the many-subdomains problem in one of the following
> ways:
The SPF record is intentionally not put at the "_spf" subdomain but at the
domain itself so that wildcards will be possible. So why not simply use
wildcards?

And if wildcards are not possible anyway (because the subdomains have any RR
records), then why is the SPF record not put at the "_spf" subdomain?

Roger