here is another online community that i earn amazon gcs from. it is called smartLAB and they are very unobtrusive. i hear from them maybe once every 2 months. all activities earn points and can be redeemed for amazon gcs in either $5 or $10 increments.
i like that the surveys and discussions are always short and sweet and they don't bombard you with activities. topics involve anything you shop for--be it financial, food or furniture! they also reward you for participation and everything has a point value. check it out!