I can't believe no one I've read has come up with what seemed to me to be the absolutely obvious explanation of why President Bush used the plural 'internets' at the second debate. Anyone who reflects on their own contemporaneous speech should understand what happened. On just my first listen to him say it, it sounded to me as if his pauses indicated that he was searching for the right wording as he put this sentence together. Perhaps he couldn't remember 'blogs'. Maybe he wanted a more general term but couldn't think of one in the short time he had before his pauses could get too awkward (and we're talking not much more than a few seconds here). He was obviously thinking in the plural, and when he realized he wasn't coming up with anything he went with 'internet', and it came out plural because he was looking for a plural. Most people do that sort of thing all the time.
An even more generous explanation would be that he was referring to the Internet and Internet2, or that the Internet is really a bunch of interconnected networks. I don't think it's a big deal if he simply misspoke.