How much is high CTR? Is 5% CTR is high? People say that google will ban you if you have too high CTR. Does this apply to your whole traffic? Or it can be apply to a certain channel? Example, if I have 5% CTR for my whole traffic, but I also have several channel that I look closely and have higher CTR like 25%. Can google ban you for that?
I think as long as your CTR is from legitimate clicks, you don't have to worry about it. Google looks at the number of clicks vs. the number of conversions reported on the Adwords side. If you're getting 25% clicks and none of those people end up converting for the adwords client, then you're probably going to get banned because it'll look like click fraud. If you get 25% clicks with a high adwords conversion rate, Google will love you and probably do a case study about you. My suggestion is to focus on providing a good experience for your visitors and keep everything legit, and you have nothing to worry about. 5% click thru is very good, in my opinion, but it really depends on the type of site that you have.
If your site is legit, if you are not doing anything to trick visitors into clicking, then your CTR shouldn't matter. There is no "should be" for CTR. You will not get banned just because your CTR is a certain number. You WILL get banned if you are doing something that deceives visitors into clicking ads.
Yeah, good advice. CTR is not an issue, if you're not doing anything wrong - you have nothing to fear.