Our service is financed by advertising on the one hand, and by our voluntary Premium Membership on the other.
It's very difficult to finance such a service solely by advertising - either we would have to show so much advertising that it interferes the use of the service, or we would have to "sell" sensitive user data in order to increase the advertising revenue. Both options are contrary to our principles - we don't want to bother you with advertising, and user data are always treated as confidential and not disclosed.
In order not to be dependent on advertising revenue, we have introduced the Premium Membership. It serves to promote our service and ensures that we can provide it for free. The Premium Membership is voluntary and is rewarded with new and enhanced features.