How long should I make my survey?
As short as you can! We'd recommend 5-10 questions at most. Depends on what you're asking, but it's better that people complete components of a larger measure over time, rather than getting them to complete a 30 item questionnaire all at once.
Are results anonymous?
Yep. This is so that your user's privacy is respected and you can gather meaningful information on engagement measures.
What if I want to send a survey where the results aren't anonymous?
Create a video card, with no video, then put some questions on the back. Crazy right?! Well, it works - we're looking at adding this feature to survey cards soon.