There is a floodgate system within the application itself that can be used/extended when developing extensions. ReFlar utilizes this floodgate for Gamification so that users aren't able to hit the API so much and spam thumbs up or thumbs down up the wazoo (The "Likes" extension can currently be exploited this way and is unfavorable to me, in my own opinion).
Correct me if I'm wrong, @luceos, but isn't there something hard-coded into core to where there is a time limit between posts to prevent spamming? I believe it's 10 seconds between posts.
Edit: Actually, yes, yes there is lol.