youtube can do this. kaltura has something, too. nice for kids and building joke videos or maybe for building your next presentation. however, pro video files

youtube can do this. kaltura has something, too. nice for kids and building joke videos or maybe for building your next presentation. however, pro video files are BIG, and upload will take longer than actual editing process with usual upload rates. More important: nobody wants to have a bloated webapp that runs in an already bloated web browser (all of them are!) and eats all your cpu power just by executing some cool javascript gui framework - you need every bit of performance for rendering.