Twitter's idea is not obvious. Why would restricting blog entries to 140 characters result in a new and very interesting phenomenon?
Larry and Sergey's PageRank isn't a new application level idea (as search engines already existed) but rather a better implementation of an existing application level idea.
Larry and Sergey's PageRank isn't a new application level idea (as search engines already existed) but rather a better implementation of an existing application level idea.