A thread at WMW starts with a pubcon snippet, that is hardly earth shattering, but is none the less worth recording.
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.
and a further addition in the thread is:-
I got the impression that it only affects sites in "certain industries," perhaps from some of Matt's subsequent remarks.
and
I was at the Q&A and listened to Matt's response. The part that I thought was interesting was that Matt said when they (Google) first started hearing about the "sandbox" as the term is used by webmasters they had to look at their algo to see what was causing it and then look at the sites it was affecting. Once they studied it, they decided they liked what it was doing.
So what I concluded was:
1. Yes, there is something that behaves like a "sandbox."
2. It's part of the algo, but wasn't necessarily created to do what it does. (they didn't set out to build a "sandbox.")
3. It affects some site and not others.
4. Google likes what it does.
http://www.threadwatch.org/node/4714