Click Fraud is a very nonstable area. Aside for obvious things like one IP making 15 clicks on your ads in 5 minutes, you know that's fake, but when industry folk who sell software to services to combat click fraud post numbers like 25% or 30% of all traffic is click fraud, that's just a guess from them, and more of a scare tactic to get you to buy their stuff. There is really no way to prove what is real and what's not. Human clicking behavior has a life of it's own. Sometimes people can look like bots, and bots can look like people. Or even so, sometimes people consider their foreign traffic as click fraud just because they can't convert it. I think the industry is just not capable of making broad claims about click fraud right now. Yes, combat those obvious tactics, definitely, but for everything else, just accept it and move on. If traffic was so fucking great for everything then no one would be selling it, they would just be pushing it to products and services nonstop to make max profit from every click.
Let's face it conversion rates are low as shit for almost everything, and when you multiply that by the millions or even billions of legitimate clicks that occur on the internet everyday, it comes down to less than 1% buy shit or click on ads everyday. So what about the 99% of the traffic? I'd put more focus on converting clicks, rather than worrying about what's real and what's not.