I've been following Munjal's account of how Riya changed course from photo search to visual search. It is a great read for all internet entrepreneurs, because sooner or later you will have to change course. That's a fact of life, and easy to say for a VC. Harder is knowing when to change course and how to do it quickly. Riya appears to have done the right things to answer both of these questions. I recommend all entrepreneurs to read the episodes of how this, now well known, startup is changing course. This is a rare chance to get a glimpse under the hood of how things are done in startups.
More links on the subject can be found on Peter Rip's blog.