I posted nearly 300 the other day, I changed one of my blogs around and nothing has happened, in fact it's search engine postioning has improved. It can hurt your blog or site as when people click indexed pages or links then they go 404. Apparently google don't like this either but to what extent I don't know?
They get listed in Google search but because of the high number it will be harder to get ranked well for these pages Like I mentioned many times before, it's better to use an hour to post 2 articles that takes 2 minutes and use the remaining 58 minutes for backlink purposes instead of using that hour just to post articles
If you are on wordpress tho and have trackbacks enabled you should get around 100 backlinks overnight, this is what happen with me. If you have a popular niche then it could be more.
you'll probably lose all your readers cos your content won't be much good. A blog is like a good meal, best savoured and appreciated in small forkfulls rather than gulped . . .
It may look unnatural in the eyes of search engines. Matt Cutts from Google have answered a similar question which you can watch here http://www.youtube.com/watch?v=JByPymBtXFY
Number 1 question would be, are the post unique/ quality content? if yes, then it will not do any harm to your site.
They must have been PLR, How I see it.... Blogspot are a business just like any other hustler on the net, it costs money to run their servers, people who are using up to much space and are not getting clicks or traffic, or are using their precious server space as link farms are pumped.... The thing about using articles is if there is another site on the web with a higher page rank then your pages will just hit the suplimental index, I you post alot of rarely used articles then the amount of trackbacks you get could give your site the boost they need, its all about PR