In social software, attention drives contribution - to a point. An increase in the amount of visible attention (quantity of explicit social relationships or activities) people receive helps drive contribution. More views of a video on YouTube encourages further uploads. More followers on Twitter encourages more updates. But this increase in production is likely to plateau.
The issue may be the kind of attention received. Focusing on real relationships can help further encourage participation without saturation. A 2009 study of Twitter explored this by comparing a user’s “friends” (defined as anyone who has been messaged by a user at least twice using “@” replies) with their followers (explicit 1-way relationships).
While the total number of posts initially increased as the number of followers increased, it eventually saturated. However, the total number of posts increased with the number of friends without saturating up to 3,200 posts. This suggests the network of real relationships (friends) is "more influential in driving Twitter usage since users with many actual friends tend to post more updates than users with few actual friends."
So actual friends (real relationships) are more likely to encourage contribution. Perhaps we can blame this on the 0-1-2 effect which states that the probability of joining an activity when two friends have done it is significantly more than twice the probability of doing it when only one has done so.
For more insights from online social relationships, check out my complete Impact of Social Models presentation.