If you have read my coverage of the Coffee Talk with Senior Google Engineer : Matt Cutts you would have read;
Q: Does the sandbox exist? A: Matt said here comes the audience part? How many feel there is a sandbox? How many feel there is no such thing as a sandbox? SEOs normally split down the line. There are some things in the algorithm that may be perceived as a sandbox that doesn't apply to all industries. He knows it works to keep some spam out.
He confirmed basically that there is a sandbox like effect for some industries. Rogerd started a thread at WebmasterWorld named Matt Cutts on the Google Sandbox which confirms this;
In reply to a question from Brett Tabke, Matt said that there wasn't a sandbox, but the algorithm might affect some sites, under some circumstances, in a way that a webmaster would perceive as being sandboxed.So, for some sites, in effect there IS a sandbox
Discuss at WebmasterWorld.

Comments:
andy
11/18/2005 08:39 am
Yeah, that sounds good. Btw, you can try the best websearch on the net: http://search.seavenue.net
AiK
11/20/2005 12:13 pm
I believe that sandbox exists not for the particular industries but exists for particular search phrases with high percentage of spamdexing. For example, there are not any sandboxes for the Russian sites in any industry. And I think there are not sandboxes even for the pharmacy sites by the rarely used search phrases that are not spammed.
Matt May
08/23/2008 04:41 pm
My industry (car hire) is highly competetive for specific keywords. New sites do well for a couple of weeks in Google, then vanish to the nether regions of the search results.
William Imhoff
05/25/2009 01:14 pm
The more you understand math the more you can relate to the comments of Matt Cutts