Today, I started fooling around with FOAF. I found a database of source and started building a database. I decided that I only wanted to download one FOAF file per secondary domain. I quickly built up an index of nearly 2000 files over 189 secondary domains.
Of the 189 FOAF files I tried to download, 87 were invalid or 46%. That's an awfully high error rate. 39 times the server returned 404 Not Found (twice 410 Gone). 11 times the remote server could not be resolved. There were a few well formed XML issues. 3 redirect issues. I'll keep y'all updated.
More: I setup my server to download new data every hour. At most one file per hour per secondary domain. Don't wanna piss anybody off. I might increase that in time. I'm gonna make the data available online at some point.
Update: Most recent stats
http://www.friendblab.com/about.aspx