I too was asked to participate. I declined as it was unclear what exactly would be sent to whom and what control (or not) I might have.
It looks like my doubts have not been removed by this analysis. Indeed I would have thought the answer to this question was good pointer to the gullibility of the user. I am a long term Yougov participant but recent changes make me suspect that the original principles are not that deeply embedded on the IT side.
A little more transparency may be necessary to maintain a loyal cross section of society.