Since the thread was bumped I thought posting this might be of some benefit for people:
Google SandBox = Old phrase/term.
It referred to sites that were "restricted" in some ways in performance, limiting their ability to do well i nteh SERPs for certain/all search terms etc.
It is Now a commonly mis-used term, as the SandBox effect that is referred to kind of disappeared sometime ago.
Instead - you may find the following;
* New sites get a short period (honeymoon) were they are "boosted" to see how they do and to get some traffic etc.
* New sites loose the HMP after a time
* Poorly structured sites may have content that ranks well to begin with, then falls due to shoddy site structure (blogs).
* Some sites have "weak" content (tiny content, partially duplciated, very poor internal link structure etc.) and may be removed from SERPs
* Some sites have a variety of Internal Duplication (Canonical, Multiple URLs, Replicated page contents etc.) which may get Filtered.
* Some sites have External Duplicated content (full), which may be Filtered out (google only wants to show 1 version!)
* Sites that are Not popular (low Quality and low Quantity InBoundLinks, and/or links that appear False/Non-Volunteered) may perform poorly
Mixes of the above are often seen as "sandboxing" - they aren't - it just seems that people will believe anythign they read without checking the Age of what they read (seriously, reading SEO articles from 2005 is not going to help you all that much unless it poitns out Quality and Originality!)