Suppose I put adsense in a hundred blogs with ten unique daily visitors each.Is that allowed?Would these crappy blogs affect the earnings in my good blog?
It kind of depends on the quality of the blogs. You mentioned that the 100 blogs with ten visitors would be "crappy", and if that's the case, your account will almost certainly be banned as a result. Google really hates it when people create tons of different blogs just for the sole purpose of getting as much incremental traffic as possible (check out some of the complaints that users have had with PrismoTube). That being said, if you created 100 HIGH QUALITY blogs that offer all the things that Google considers "valuable" (though what "valuable" really means to them is debatable), it would be kind of hard for them to justify banning you. If, however, they are poor quality and offer very little by way of value to visitors, it won't take long for Google to notice what you are doing and ban your account altogether (even if some of the blogs are actually good). On a separate thought, I'm somewhat skeptical if you would even be able to manage that many blogs under a single AdSense account. Google might view your sites as being a part of some kind of "network" or content farm, which would give them every incentive to kick you off the adsense platform. The only reason I bring this up is because I know some people who have actually been penalized for having too many sites connected to adsense, and Google sent them a letter saying that they violated adsense policies and/or webmaster guidelines. Just something you may want to take into consideration before moving forward with whatever you're thinking.
You could not maintain and update 100 blogs so this is a silly question. It would be much easier to update ONE blog and receive 1,000 unique visitors across the blog a day by adding unique quality content than it would to create dozens of blogs that are rarely (if ever) updated. You should be thinking "What if I created 1 quality article a day on my blog that eventually received minimally 10 unique viewers a day. After one month potentially I could receive 300 visitors/day." This is all it takes to receive traffic. However, most people will never see success because they lack the motivation and inspiration to be CONSISTENT and DEDICATED. Good luck.