The default random-node code could use some tweaking... To that end, I created a bit of a workaround that you might be interested in at: Random NonHome Nodes
Not only will it prevent you from landing on a "Permission Denied, Tough Beans" page, it allows you to selectively weed out sections you aren't interested in. It even avoids the a large number of the empty homenodes for you.
Personally, I'd love to see a "Random Thread."
-- Yeah, I'm a Delt.