These days more and more people making highpaying niche site. They just collect info from other articles and sites and make articles and site. I think its called MFA. I saw a blogger who had adsense on his Mesothelemia blog. And few months later it was showing PSAs. So he got banned. Now the question is it risky to make highpaying niche site??
It's not risky if you go with original content and you know what you are talking about. It's really hard to rank well in these niche and I simply avoid them. I don't avoid them strictly because of competition, but I do avoid them because I'm not passionate about Meso, FOREX trading or whatever paying niche it might be. Writing content and building backlinks for something you're not passionate about and you don't care is hard and in the long term it's not worth it. On top of that, if you go strictly MFA, you can bet banned.
There is nothing wrong on writing a blog and earning thru adsense in a high click rate topic. As long as you are following google adsense TOS and you are enjoying on what you are blogging.... Go for it. =)
It is risky for you to build an house while starting by the roof... Clear your mind and think as a human: - what do people need? - analise competition - create unique content - create a fantastic site - earn some cash while helping users This is the only way to go.