My guess is that the professional community, people that earn money manipulating/contributing paid-content to Reddit, is quite big. Or, at least, their impact is really big. Most people are just readers and Reddit professionals have time, motivation and knowledge to game the system.
I have fun reading Reddit. And I read it very often. But, I do not trust all the enthusiasm about any movie/service/app or similar that the community generates. It is usually over the top and not very useful to actually get a good idea of the quality of such a product.
I think that as a society we need to develop new mechanisms to deal with the situation. Probably regulation is one of them. But, for people to able to understand that not everything in the internet is true is also important. It will take time, people still think that reality shows are real, but I think that is feasible.