Managing an online service with a good little number of users who are pretty happy with the service, I am considering adding a "Donation" button to partially cover my expenses.<p>Since this is some extra work to implement, and this can provide a deceptive experience, I wonder if it is worth it.<p>Has anyone implemented this before?<p>How much money / user did you receive?<p>Would you do it again?<p>How does it compares with ads revenue?