I wasn't necessarily talking about diffing on the web. I was actually talking about a diffing service.

I've seen lots of diffing programs and they all seem to have varying levels of success. I think there's an opportunity for a company to become the gold standard for diffing and to offer their diffing engine via a service that can be integrated into apps (web and desktop).

I bet there are lots of app developers who would like to have a robust diffing engine in their apps, but don't have the time or expertise to build one themselves.

EDIT: I see that you're the author. Have you thought about putting your diffing engine behind a web service?