But what really is "natural" according to Google and how could they detect it?

There's probably a few different patterns that would look "more natural" to Google. And I'm guessing it isn't black/white, but Google probably assigns a percentage of some kind, maybe like:

Link pattern = 77% natural.

This is just a made up example for the sake of discussion, but we can probably be pretty confident Google does try to detect natural and unnatural linking patterns.

One possibility is an "explosion" of traffic. This could be caused by being on Oprah or other big media exposure. But if this is the case, it would seem that certain types of sites, such as major entertainment sites, would be the first to report/post this thing. And if they're not first, they'll be close behind.

If this is the case, then it would seem that if you want a lot of links very quickly, you'd want to get some "press" from some very major sites to justify the quick explosion.

Another natural pattern, and maybe the most common it would seem, would be to see a site get a few links the first month from places like directories and "cool" sites, etc. Then the social sites start a trickle of discussion.

This builds slowley at first, then picks up speed, with social media, blog comments and more all creating links.

Then link velocity will plateau after a while (week - months), then trickle off.

Think about this from Google's point of view...Why did all the social media like Twitter, Facebook, Digg and other sites start giving you tons of links all of a sudden? How did they find you?

If we believe in the "natural growth theory", then maybe a strategy should be to order the types of linking you do, as well as the numbers.

For example, maybe start with a press release and a few directory links. Then a few scattered Tweets, a couple of forum posts and blog comments.

Then lead with a growing number of Tweets, Facebook mentions and become a lot more aggressive with your over-all linking strategies.

This is far from being fact and should only be meant to get you thinking about how Google may detect natural/unnatural linking.