I agree it may be a nice touch on an already useful feature, but for me it seems a bit redundant in that you already have control over who you send the link to. Considering that Sindre has also added the ability to limit the time that the link is active and you can also delete the link at any time does give you quite a bit of security already.
For my psoted response, I just set it to be active for 1 week, then it dies automatically.
Glad you appreciated the response, I just couldn't help myself.
There's always more to learn ...