Another of the great debates in the world of internet marketing revolves around the "safe" speed at which to build back links.
There's a school of concept that states that Google loves natural, organic link building, which is to say that it doesn't appear natural if a lot of links emerge quickly for your blog (which you DO usually get when using some sort of article spinning software along with an automated submission routine), and then a dearth where you see almost none. Another factor of this natural, organic link building is to generate links from various different sources: article directories, web 2.0 properties, forums, other websites, personal blogs, and so on.
This then, leads to a philosophy that says that it's wise to moderate your link building. Do it in calculated steps (that would lead one to naturally turn away from article spinners) to stay under Google's RADAR, and slowly grow your links over time. Some people out and out mention a figure: "Don't add greater than ten new links a day" or "Anything under 50 and you should be fine." That kind of thing. At the end of the day however, whatever number is given, the principal line of reasoning is the same. If you add so many links to the system, you'll run the risk of winding up in Google's 'sandbox,' and irrespective of how many links you build, you will not rank good until your time in the penalty box is up.
At this point, Google hasn't out and out admitted to the existence of a 'sandbox,' but there's some compelling reasoning to this argument. Again, it's best to be safe than sorry, and I suspect that this generally careful approach is the primary reason why the "drip feed" strategy to link building seems to be the dominant approach on the web at present, and if you study your websites, you can almost see patterns (for example, you'll often see a "Google Dance" on your sites right after a major link building push as the system digests a slew of newly discovered back links--often made worse by the use of article spinners-- and does whatever it does to determine how this impacts your overall rankings state).