The ideology behind Open Science is to transform the masses into a scientific workforce and motivate millions of people to work together. They are distributing content like the dancers on the Love parade in Berlin which has over 1 million people on the same time who are collaborating. But, do we need such amount, or wouldn't it enough to mobilize only a small amount of people?
The famous Artificial Intelligence forum https://ai.stackexchange.com/ has only a limited amount of regularly users. According to the last statistics, in the last year only 50 people have posted some content to the forum. Surprisingly this small amount was enough. The forum contains lots of answers from different subjects, and incoming new questions gets an answer reasonable fast. The hypothesis is, that 50 serious users who are contributing to a forum or an academic journal are enough to bring a discipline forward.
Suppose we have 50 users, who are writing academic papers on the subject of Artificial Intelligence. Each user is able to write one paper a month. After one year, the group has produced 600 papers. It is not a second Arxiv.org repository but it is enough to bring the subject forward. So perhaps the ideal Open Science community consists not of million scientists, but only of 50? The question is not how to attract the whole planet to attend an online forum, the question is what the upper limit is. I would guess, that https://ai.stackexchange.com/ can handle perhaps 200 users who are posting questions and answers there. More wouldn't improve the situation but result into chaos. Today's 50 users are a bit small, but it is not advisable to increase the number to 500 or even more.
I would guess, that in other disciplines like economy, literature, biology and medicine is the situation equal. A single researcher is not able to run a forum and a journal, but 50 people who are working together are more then enough, and increasing the number of scientists to the range of 1000 or more would not help to improve the situation.