GraffittiBlogs are Dynamic Blogs where users must post daily to stay on thread. So the Thread is like 5 posts long and newest post overwrites the previous 5th post.
Comment.it or Comm.it would be good domains for the other idea of a URL shortener like YOURLS combined with a commenting feature and web frame.
I had a similar idea for shop-stop a dot top domain for shops to build keywords to their website. in short you can now right click on search forms and add keywords to simplify searching altogether so SEO that! I can search youtube like so "y art hollywood" to hear a song I like -so easy a monkey could do it or "y nico d star"