Buy/sells seem to be only time stamped to a day. Surely you need greater accuracy than that, e.g. the exact second? Otherwise, if I buy a stock on a day where it rises 10%, what price do I get?

Do you take dividends into account? If not, why not?

How do you rank people who make different numbers of picks? A naive method would be to add up all the returns, but this would then favour people who make more stock picks. For example, if I recommend two 'buys' that both give a 10% return, have I gained 20% in total or 10%? (As I would have had to split my bank to invest in both at once)