Heh, measuring average and unbiased user opinions on the internet is probably the second most uncertain thing in this universe after actual uncertainty in quant

Heh, measuring average and unbiased user opinions on the internet is probably the second most uncertain thing in this universe after actual uncertainty in quantum systems. Both opt-in and opt-out ways of doing surveys on your website introduce bias. The opt-out (read: in your face pop-up) is more likely to make people angry which makes them more likely to leave negative reviews. The opt-in version will only be found by people having a relatively extreme opinion about your site, good or bad. The difference being in the quantity of the data. The first will probably be answered by more people, since the people who'd have completed the survey in the second case are probably more or less a subset of the people who would complete the survey in the first case. All of this makes it no surprise that most websites that want to have any kind of feedback from their users go for the opt-out strategy. More is better if less is not in any way more :)