How does google detect blog farms?

I'm talking about where someone buy hundreds of domains, installs bloggs and then uses "spun content" to pad it out with seeminly unique content.

Usually each blog in the blog farm is has some links generated to it through social bookmarking, article submission, meta links, directories etc....

When you have a hundred or so blogs in your farm and you put index links across the board it can be amazing boost to rankings for the site you point at.

I see so many of my competitors using this successfully but it makes me wonder how google will be able to detect it?

Google has their Own Alog's to do so,They are a Company that has bundles of Talent with respect to Staff.
As well as a huge Culture where people don't Like any sort or malpractices.
Google are also very secretive when It comes to Exposure Of some Of their Practices.
This Is one Where they don't want exposure.

If sites are not interlinked, class c ip's are different and content is spun, how can they detect it? Seems like the real money these days is made by creating blogfarms. As long as you don't get greedy or careless it is difficult for them to catch you.

Now the blog is still effectively, but not important as before.

Google reduce the blog rank several days.

I think Google can detect from the ip addresses but if the ip addresses are different its very difficult to detect..

yeah u can get seo hosting with diff c class ip's and it would certainly help you if u wanna start one

if you gets 1000+ BlogPost with all Different IP's it's not spam and Google Gives you rank as well.