I didn't expect to post anything besides my scheduled meta for a while, but this is important. I want you to take note. Yes, you. Are you even vaguely interested in creativity, as a producer or consumer? Great. Read on.
Kindle Worlds is a Bad Idea. You can read more on this topic at A Response to the Kindle Worlds Announcement.
Please do not participate in or support Kindle Worlds.
The contract terms are bad. What you sign away includes but is probably not limited to: all of your OCs, the right to post the fic on your LJ, and the right to decide whether the story gets to stay up or not.
The content guidelines mean your fic probably doesn't make the cut. Crossovers and porn are both disallowed. I'll explain why this is a concern in a moment. Additionally, so are drabbles and most lengths of flash fic.
Fandom is a gift economy. Does this mean that free fanfic is Just The Way It Is and that being paid is unacceptable because it's a breach of tradition? No, not at all. What it means is that fandom has some unique cultural aspects that are, in my opinion, worth preserving. That culture is tied to fanworks being free. Could some aspects of it be preserved anyway? Almost certainly. However, I would advise exercising caution before taking that risk.
This could hurt professional tie-in writers. Why undercut their prices? This might convince rights-holders not to license tie-ins for better compensation, if they weren't already this cutthroat.
This might hurt fans who write for free. It might or it might not. Why might it do so? Suppose Fan X agrees to this and publishes a fic this way. The canon rights-holders benefit financially. Suppose Fans Y and Z don't want to, and keep posting their fic elsewhere. Fans Y and Z are already not helping the canon rights-holders (this is not true-- they recommend the work to others-- but canon rights-holders usually undervalue this service), so it doesn't harm the rights-holders if they're forced underground; on the other hand, it benefits, the rights-holders if they agree to participate in this new system. Fans Y and Z might be getting cease and desist letters.
If that does happen, it hurts creativity. Remember that they don't allow crossovers or drabbles.
Is this likely to happen? Probably not. I suspect this will fizzle and die because everyone realizes how bad it would be otherwise.
Source:
http://chordatesrock.livejournal.com/45571.html