I've seen some peoples who saying that they got some warnings by email about minor/major issues regarding their site contents/activities all these before the ban but I've also seen many peoples saying that they got banned right-a-way without any warnings!! so why some and not all. I personally believe that Google should issue a warning if it happened for the first time and let the site owner to know about their issues and fix them asap, as sometimes things happing with out you know about it.
Who knows? Just follow the rules and don't worry about it. People should get banned instantly if caught breaking the rules it's not like they are hard to follow.
I know people that have been sent warning messages and others that have just been cut off. Google seems to do whatever they want. Your personal beliefs don't matter to Google.
I had a website designed once and gave the designer my adsense information to add ads. He was a stupid idiot and clicked ads - Google emailed me about that. Sometimes I notice clicks for £00.00 and assume they are from PSAs or because of suspicious clicks...
that depends on the severity of the violation. if it is one or 2 accidental clicks by you, then you will get warning. but if it is bot generated clicks, then immediate ban without any warning
Google needs to improve on the communication part (support, adsense, etc). I sent them an email to support and never heard back!