Google has claimed no grievance with Infinite SMS other than its success. Their given reason for the block isn't abuse or wrongdoing; it's that we brought too many users (and thus too much cost) to an experimental service.
Naturally, this means that the Infinite SMS app for the iPhone / iPod Touch has also been discontinued. The good news is that the proprietary SMS service are still available in Labs, so it's not a total loss. Still, users of the popular Infinite SMS app will undoubtedly be disappointed. [Innerfence via TechFlash via CNET]