I believe times without number some top members have made little mistakes that is against the forum rules and they served the consequences. It will be too bad if will keep on falling fall little mistakes. New members let's try not to learn from our mistake because if we do ,it maybe too late to correct it .
Remember that these 'little mistakes' that you mentioned (e.g. plagiarism) is against forum rules. It is posted on the rules on the forum. Whether if someone reads the rules or not, constructive notice is enough for liability to attach to people who violate such rules.
But I do have to agree with you that experience is what separates a newbie from a veteran. Experience teaches you something to absolutely avoid since a person has experienced it personally.