Eharmony is very unique when it comes to dating agencies as they try to offer more than the rest. They want to save you time so that you don't have to mindlessly navigate through 1000s of incompatible profiles. They directly match you with who is most compatible and from there you can decide if you want to contact that person. Eharmony accounts for as much as 2% of US marriages so this approach seems to work well for them and for members of this highly prolific website.

More about how scientific matching works:

With over 20 million profiles something needs to be done to discover which people are going to become compatible. When you initially sign up you fill out a form that looks at a matching system that involves 29 dimensions of personality that are needed to form lasting and fulfilling long term relationships. These include anything from your beliefs regarding marriage, to your religious faith, if you smoke or not, are a recreational drug user, to what kind of vacation you like to take. 

Once all the variables and accounted for, and based on location, you are then offered the option of contacted a selected number of matches. You can choose to contact these matches at your own pace. You can ask these matches from several popular questions that are meant to get into the heart of the matter, or else you can bypass the system and simply send them a regular email type communication.