Whitey - 12:44 am on Jun 7, 2010 (gmt 0)
My sense is that a de indexed site can involve a manual review. Once the effected site is flagged by an editor , the effect will be held as part of the algorothmn in the site's history for any transfers , along with any other profile information on the owners or related sites. The only way out of this is to fix the problem , seek a reinclusion and hope.
For a penalised site such as the -50 , it might be slightly different and rely on an algorithmn for minor things or a combination of algorithmn flagging and manual reviews - especially in competitive verticals where the index is being constantly reviewed and reported on. Redirecting this may not hold the same risk if the offence is minor, but it is still a risk, so 404'ing the old pages may be wiser. The more aggressive the penalty and site practices , the greater the risk.
There have been several comments by members that Google does not do this algorthimically because of the risk that a competitor can redirect a badly penalised site at a competitor. This wouldn't be fair. So my hunch is very much that Google takes precautions before doing this.
Quite how they do it - of course i have no idea - since it might involve some complexity to combat the tricks of such tactics. It may even involve some escalation to higher editorial control levels.
Often webmasters complain that spam reports were not acted upon for many months , if ever - and this further plays into the notion that it involves a heirarchy of priorities. Again , popular verticals and high traffic sites , for example, would take priority ( i would have thought )
I have no testing knowledge, nor seen any proven reports of this, so I can only speculate.