This is the final answer of a ONE year old problem, appears after the August 2010 CU (see http://blog.hametbenoit.info/2010/11/30/sharepoint-search-results-not-complete-with-august-cu/, http://blog.hametbenoit.info/2011/01/04/sharepoint-august-cumulative-update-issue-with-anonymous-search/ and http://blog.hametbenoit.info/2011/04/08/sharepoint-office-web-apps-anonymous-access-and-search-results-final-conclusion/)
The SharePoint Product Group has finally provided a fix for this problem with the June 2011 CU (to be deployed after the SP1).
With this fix, Office document published on SharePoint sites with ANONYMOUS access are now back in the search results – what ever you use the SharePoint Search engine or the FAST one.
Anyway, there is a limitation: if you click on Office document available anonymously, you will have an authentication prompt; if Office Web Apps are available, there will be a link ‘View in Browser’ which allow to open the document anyway.
Be careful, by default, the fix is NOT ENABLED.
To enable it, you have to set the property ShowResultsWithPartialPermissions to 1
You can do with PowerShell.
$app = Get-SPEnterpriseSearchServiceApplication
$app.SetProperty("ShowResultsWithPartialPermissions", 1)
$app.Update()
If you have more than 1 search service application (as this is the case with Fast), you must adapt a little bit
$app = Get-SPEnterpriseSearchServiceApplication
$app1 = $app[i] // where i is remplaced with a value between 0 and (nb of search service application)-1
$app1.SetProperty("ShowResultsWithPartialPermissions", 1)
$app.Update()