What is the goal of the social application you want to launch? Do you want to gather data for each of the user who will go through it?
According to those goals, you can set up a custom form, asking users data – see the data you can request in a form.
The form is not required if no prizes can be won. On the other hand, it becomes mandatory when the user agreement must be accepted by the user – see Submitting terms & conditions.
The same form is used for applications visible on the web and mobile. Fully customisable via Nuke Suite, the form is only displayed to the user once and is valid for all subsequent participations.
Last but not least, you can customise a form for each of your users using Smart Data Capture.