There are tons and tons of "web annoation" tools and services, but none have ever caught on. What makes yours different, and who is your audience?
My audience is anyone who reads in the same way I do. I often want to snip a paragraph from an article or paper and have a quick way to browse through my recent snippets to refresh my memory on what I've read.
I don't really care about "social" or seeing community highlights. I just want something to help me digest material faster.