FYI: There is no daily limit. Maintain quality of your posts and only make on-topic posts. You won't be banned. People listed above were banned because some of their posts weren't really on-topic.

   -MZ

Everything is subjective, sometimes 100 meh quality posts spammed in a 1 day time frame catches a moderator/admin's attention more than 10 poor quality posts. There aren't post limits, however it goes without saying that at a certain point its hard to maintain post quality. People aren't banned on a whim, time is spent investigating especially in these situations where it isn't copy and paste/quote/smiley face/ +1 spam. Sometimes people spam meh - ok quality posts, but when you read the threads they are posting in, their posts aren't completely related or they are just reiterating prior posts to get the post count up or they are posting in threads that have already drawn a conclusion, and they are just reiterating points. People that post very frequently especially those with paid advertising signatures catch more attention sometimes than small spammers. Trust has no impact on bans or ban duration, while admittedly account age/status does minimally if I'm being honest. No one has a free ticket to spam, but a newbie with 5 of 10 of their post count being low quality are more likely to get a severe ban, than a member who has been active and posting high quality posts for a while, and slips up and spams a bit.

As I said, there are no rules on post count, you can post every 10 seconds if you wish, but the chances of your posts being quality decrease when you impose quotas.