I have to say I don't get it.
Tumbleblogs, okay, I get. As you go about your day finding interesting quotes, links, images, videos, etc. you repost them to a blog and share them with the world. No original content required - hell, there's barely even effort required. Or even sites like Delicious or Digg, where you're doing little more than bookmarking a link for all to see, maybe with a little comment.
But retweeting? CAN'T YOU THINK OF 140 characters of your OWN!?!?
Look - Tweets all have unique URLs, no? Why don't you just bookmark them instead? Or better yet, why not use the feature that's *built in* to Twitter and just mark them as your favorite? Then I'll subscribe to your favorites if I want. Here's my Twitter favorites feed. It's completely empty because I never use that feature, but I will now if for no other reason than to show how to not re-tweet stuff.
I guess, hey, just like it's your blog, it's your Twitter stream and you can write whatever you want there and if I don't like it, I can just unfollow you. But obviously, if I'm following you, I want to know about what you're doing or thinking... not what *others* are doing/thinking but what you are.
Just a thought.