Mike wrote:
...look at this snippet of XML from enwiki-latest-pages-articles.xml.bz2 taken from late August. I don't see any namespace in the <title> elements, ... <title>AaA</title> ... <title>AlgeriA</title>
Those are main namespace (namespace 0) articles, so they don't have a prefix. But all the non-main-namespace pages do. The first is <id>724</id><title>Wikipedia:Adding Wikipedia articles to Nupedia</title>.)