Hi,
I am representing a start-up website
http://www.hotelgo24.com. We are currently performing usability evaluation of our website, where our users fill in some questionnaire and complete tasks on our website, it takes about 5 minutes to complete it. So far we have rewarded participants of our test with 5mBTC. But we thought of another idea, that for each participant we could donate some money to charity organization. Our proposal to such charity organization is that it would advertise this evaluation on their website and/or social media pages, and for each participant we would donate some mBTC to its account.
We want to promote BTC and work closely with charity organizations (for example donating some BTC after user books a hotel room), so this could be a long term partnership.