Seems a cool idea to use with mockups and prototypes, but an awful idea to use in a serious product.
Leaving my front door open when I'm on holiday also makes more things possible. That does not mean I will like those things.
But if you have a blog and you would like to constantly display some specific content from a different webpage via ajax it seems like the easiest & most simple solution.
What happens to my application, if your service goes through a DDoS? What happens to my application, if you suddenly decide to close your service?
I'm pretty sure you can use these arguments about other services, but this service exactly, is not worth the risk.
I just don't trust it enough to use in production.