And that's why I want to go re-read it now, but sleep will come first before I do that...

The theory I had actually wouldn't have been true now that I think on it more. The theory as I said in another comment had Gibbs using Shannon's collar in trade for Tony's... That wouldn't have been a good start to their new relationship thinking on it.

That would have been Gibbs trading Shannon's love for Tony's. Tony is not Shannon and he needed to make Tony his, completely and with nothing from his past love "tainting" it. Taint isn't the word I want to use, but I can't think of what I really want to say there. (darn, thesaurus isn't helping find the word I want... *pouts*)

So it's best what he did do...