I think twitter is a great example of this.
Disclaimer: These are all just my assumptions.
I saw this video where the creator of twitter talked about the product's inception. They were actually working on another product and in the process of working on it they created a side program that simply served to help the process. Twitter was built to be used around mobile devices so they can shoot short messages to one another to better coordinate their collaborative efforts. The program turned out to be so unique and interesting they ended up releasing it to the public.
So here's what they didn't do when twitter was unleashed to the masses. They left it open ended and wanted its users to define twitter's ultimate functionality. So it was never specified that you should synchronize it to your phone. People set up their accounts online and started using it behind the computer, naturally, and here are the result.
Twitter is a program designed around mobile phones, specifically to be used in group coordination and sharing relevant information at the inception of a need or thought at the instant of its necessity; because it needs to be heard then and there so that others may share in that experience as it plays out. Anyone who uses twitter is aware of the junk feeds. But why is that information junk or associated with spam. Mobile social networking is all about the necessity and relevance of information at specific points in time, but when users are on twitter behind the computer they treat that information differently with regards to time and its suggested relevance, which is lost with time. They don't recognize that in the span between 1 minute after a tweet and 10 minutes after a tweet that information lives out an entire life and dies, and should that information hold no temporal relevance whatsoever, then it never held any relevance to the world of active listeners experiencing the world at its very instant anyway.
So to answer your questions with regards to early release.
My idea is that the two dominant functions of twitter, behind the computer use and mobile synchronization, are counterintuitive in the way its relevant duration of content is treated by its users. And I believe that it's because of this functional ambiguity that has triggered such mass appeal, incredible growth, complete incomprehension of its underlying functions, and thus its notorious drop off rate of over 60% (which I would actually put at 80%+).
If you put it out early before it's really defined, you might actually get more people to use it than putting it out with specified functions appealing to specific demographics. However if you run into a situation where the users are stepping on each other's toes they will leave and all you'll end up with are a bunch of unused accounts with birds for avatars.
That's just one scenario.