On every SEO forum, you will find discussions and arguments about the theory of a Google sandbox. In its most basic form, the sandbox is a term used to describe the inability of new sites to rank well in the SERPs. Exactly what the term means, whether or not it actually exists (or is an excuse for failure to rank), and what the causes and workarounds might be is one of the most discussed topics in SEO today. We all have our opinions, myself included, but there has not yet been a consensus on any of the factors. Not even everyone can agree on what to call this "thing that may not even exist".
One man, Randfish (his forum nickname), has compiled the history of this theory into one nice article. You can find the article at www.socengine.com/seo/guide/sandbox-march-filter.html. He gives a comprehensive view of each of the different arguments that have arisen out of the Sandbox theory. It is well worth a read. After reading this article, you may be able to come to a firmer decision on which side of the Sandbox fence you sit, and you may even end up finding your way out of the Sandbox - assuming, of course, it actually exists!