Participation in these surveys or contests is completely voluntary and you therefore have a choice whether or not to disclose this information.

参与这些调查或竞赛是完全自愿的，因此您可以选择是否披露这些信息。

youdao

One of his key take-aways: The most popular company profiles were those that engaged visitors with contests, surveys and special offers.

WSJ: Make Social Networks Work for Your Start-Up