I might be wrong because I am not an expert but I think that referals are not a good form of advertisement. Considering that not all will probably will be interested to do a lot of signing in or posting of links, the end result will be that only a few will know about the idea or project. Where as a direct to the mass form of communication i think is far more better because it diesn't have limits or boundaires. In the referral method, when somebody is not so interested, communicating the idea or a project will be stopped to those types of people and  gets filtered. So communicating the whole idea is then limited.