In addition to DdmrDdmr's quote above why there is a merit sources to send or pump new merits into the system or to the merit sources where merit sources are the one who will send the new merits to merit worthy forum users who really deserved getting the merit that all of us can could be able to earn it.
There are 130 merit sources with a total merit generation of up to 20895 sMerit per 30 days
The reason why there are so many merit sources is because it will be very hard to earn merits especially if the merit source is very strict on his/her criteria for the post he/she wanted before you'll get your merit so, if there are 130 merit sources then there will be different criteria that you can actually meet the requirements. Another reason why there are 130 merit sources is to make the merit distribution faster than having one merit source.