Couldn't get on the Internet for a while last night, because all of Comcast's DNS machines went down. Had a working connection, but there was no name resolution. Fortunately, I was able to VPN into my work machine, since that's all done with IP addresses rather than names, and Google for the address of a public DNS to use as my secondary.
And just in case, I'll be putting a few sites (Google, for example) into my hosts file so I can get to them in the event the secondary goes down as well.