This is not quite private as anyone can tag a bookmark with your “for” URL which populates your “for” account, there is also a private feed (for your eyes only) so you can keep up with who is sending you stuff…so anyone can contribute, but only you can see, so it’s semi-private.
But as John points out, there is no way to filter this stuff in some sort of queue, like moderating comments in a blog.
The reason I say this is that you may be re-syndicating stuff from your “for” account onto the sidebar of your blog. Robin Good has people (the NewMasterMedia readers) bookmarking stuff to his “for” account which creates a great stream of current stuff, so he has decided to share these findings (which have been shared with him) by re-synidcating this content on the sidebar of his blog…he also shares his private “for” RSS feed so you can keep up-to-date as it happens (very unselfish of him).
So you can see that if you are re-syndicating this content, it would be good to have a filter before it went live, in case of silly spammers indirectly publishing spam to the sidebar of your blog.
Why not just use one of your tags (user level), well you can, but that means only you can bookmark stuff in this tag, what about if you want others to also contribute…well just make a general tag at del.icio.us, but make it unique enough so no one else will use it…fine, but this isn’t private enough, there can still be a chance of noise.