I couldn't agree with this more, opening up a general API would be a great step forward for IFTTT.
I recently also wanted to add integration with IFTTT for something I am working on. However, instead of writing a blog post and putting it on HN, I contacted IFTTT. They responded very quickly and were interested in helping me add my own channel if my project became a product. While this may not be as easy as providing open webhooks, I think it's a viable alternative which better fits their model of being focused on the end user, not developers.
I recently also wanted to add integration with IFTTT for something I am working on. However, instead of writing a blog post and putting it on HN, I contacted IFTTT. They responded very quickly and were interested in helping me add my own channel if my project became a product. While this may not be as easy as providing open webhooks, I think it's a viable alternative which better fits their model of being focused on the end user, not developers.