I am blocking the snippet bot also, and apparently some other form of a googlebot. Need to do some access log checking to figure out what it might be. In GWT now, they show any crawl errors along with server responses broken down by Desktop, Smart Phone and Feature Phone. I'm blocking Feature Phones somehow, but it does not show a 403 response, no response at all. It is about #122 on my list of things to do right now. I just copied the list of URLs they say they were blocked from and the datestamp shown.