They're not allowed:
"Ads cannot require viewers to click on the ad to submit Personally Identifiable Information (such as name, date of birth, phone numbers, social security number, physical addresses, or email addresses) on the landing page or in the ad, except to enable an ecommerce transaction and where the ad and landing page clearly indicate that a product is being sold."
and
"Ads cannot offer incentives to viewers for clicking on the ad, for submitting Personally Identifiable Information (such as name, date of birth, phone number, social security number, physical addresses, or email addresses), or for performing any other tasks."
If you're doing them, it's going to be a short lived campaign. If they haven't caught you yet, they will. Unless you're cloaking of course...