If I were writing a social network layer to a creditworthiness algorithm, the first thing I'd do is create some kind of taxonomy of friend networks. Got 500+ friends? See if the Google results for your name indicate fame (i.e. you show up in title tags on Amazon, IMDB, or the NYT). And bam, reduce the social networks' weighting.

Although I would be willing to bet that a) your fans will have above-average credit scores adjusted for age, and that b) authors whose fans have crappy credit are themselves more likely to have crappy credit.

In the extreme case, if you're a law professor and your FB friends are all attorneys who loved your book, you're probably a good credit. If you wrote a guide to how to fool your parole officer and your FB friends were all fans of your book, your odds of default might be pretty good.