Google ban several blogspot domain

I don't know why, but recently this 3 month, many blog of my friend is banned by Google. Some of my friend says, the blog is banned by google because the blog content is too much spam and too much ads. But why google hate spam and over ad display?, i think for spam is normal because it's disturbing the web, but for too many ads, i think it's because too many ads it's like not a normal website, or it's just like a spam, because when visit the site with too many ads, it makes that website looks like focus to the ad and not focus to the content. Conclusion, my opinion, if you have blogspot, don't add too many ads to your site, just add some ad maximal 10, don't do copy paste from another blog, don't posting an article more than 5 per days.