Woz answers that in iWoz -- the details of which can be read on Wikipedia: http://en.wikipedia.org/wiki/IWoz. I don't think he's active anymore.
"they might be more likely to do business with other Freemasons"
How does that differ from any other social, church, or civic group? You know these people better than you know some random person in the Yellow Pages, so it makes sense to go with the safer option.
" It also bothers me that it's so pervasive."
Can you elaborate?