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

We may use a third party service provider to conduct these surveys or contests; that company will be prohibited from using our users' personally identifiable information for any other purpose.

我们可能会使用第三方服务提供商进行这些调查或竞赛，该服务商将被禁止出于任何其他目的来利用我们用户的个人身份信息。

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