What are those members not infected with?  Common sense?  What people should do is read the rules of bitcointalk before ever making a post.  That way no warning would be necessary, and I don't support giving warnings out anyway.  Most bans lately have been for plagiarizing content, and anyone should know that's not the right thing to do--not on bitcointalk, not on any forum, not in college, not anywhere.

That's because idiots are too lazy to read anything, because they're too busy making posts for shitty bounties.  That's one of the reasons why they get banned first and learn the rules second, and it's why they're ignorant about the merit system--and why merits are so important to them in the first place. 

Having a warning system would only add work for the mods, and it's not necessary.  Why should mods do more work when noobs can't even be bothered to read the rules and all of the threads about the merit system?