I don't think emulating Keynote is the right play. Any online presentation app should be designed to exploit the inherent advantages that web applications have, i.e. collaboration, information retrieval, etc..

I don't think the goal is to replace Keynote or Powerpoint but rather provide software the lets people easily develop bring presentations for a web audience.

As a former iWork engineer, I think some of the stuff Keynote has can't be replicated effectively in a web application.