While I can understand life in general getting in the way of an immediate thank you, I'm pretty sure all of us can find a second or two to send a thank you pm to their SP. If you didn't like your package, that's no excuse to not acknowledge that it came, is there? I know our mail lady does some bizarre stuff with our mail and so I'm not 100% sure a delivery confirmation means the package was given to my SP, just that it was delivered somewhere.
I would never dis a package, but I will always acknowledge it got here and thank my SP. I like including a little note about me, who I am, what we do, etc to increase the friendship part.
And no, I would hate to see the swap go away. Even tho this is only my 3rd month at it, I have enjoyed putting together my packages a lot. I have a lot of fun, trying to stay under $10 while pulling things from my stash, from discount stores and places like Harbor Freight, Tuesday Morning and quilt shops with coupons.