minimax, the Zidisha statistics page significantly understates the amount the average lender will lose, which is in fact closer to 30-35%. The Zidisha stats page performance is steadily declining toward that end.
In the hypothetical case you describe, making 10 loans of $1000 each, you would expect to make $500 in interest but lose about $3,000 in principle to default over a 12-month period. Individual results have been both somewhat better and worse than the 30% number.