It's more of a chronic problem than a sitedown problem. You might be surprised how crappy some hosts and resolvers are. Using dual 3rd-party DNS does give you

It's more of a chronic problem than a sitedown problem. You might be surprised how crappy some hosts and resolvers are. Using dual 3rd-party DNS does give you one very good advantage in acute situations, though. When your host goes down hard you can still repoint domains, receive email, etc. In general I recommend dispersing services: put your company's blog on a subdomain hosted somewhere else like Weebly, and use something like Google Apps to handle your domain's email routing.