Best Bets created for sites under one site collection are not being reflected in the search results for sites in different site collections.
Best Bets are only associated with the site collection under which they were created.
This may appear to be unexpected behavior, but it is the intended design of the product. Best Bets and Visual Best Bets are only associated with the site collection under which they were created. Below is an example of how this is designed to work:
Site Collection 1 – http://intranet.contoso.com/sites/demo1
Sub Site – http://intranet.contoso.com/sites/demo1/search
Site Collection 2 – http://intranet.contoso.com/sites/demo2
Sub Site – http://intranet.contoso.com/sites/demo2/search
Based on the above example, there are two separate places to define Best Bets and Visual Best Bets: one under site collection 1, and another under site collection 2. Both will share their Best Bets and Visual Best Bets with their sub sites (‘demo1/search’ and ‘demo2/search’, respectively), but not with each other.
If it is desired for the Best Bets and Visual Best Bets to be added in one place, and have them reflected in all the sites, one can proceed by either of the below methods:
1. Create the additional sub sites under the same top-level site so that they are within the same site collection, and therefore can share the Best
2. Continue to define the Best Bets & Keywords under multiple site collections, but configure a PowerShell script that will periodically synchronize (copy/update/delete) all the Best Bets/Keywords/etc. between the two site collections. The PowerShell script will perform the task of syncing (copy/update/delete) all the Best Bets/Keywords/etc. between the two site collections.
Information regarding how to create the scripts for importing and exporting the Keywords, Best Bets and more using a CSV file can be found at the below pages:
Script to export – http://gallery.technet.microsoft.com/scriptcenter/6b9b2e1c-7521-4091-b2a0-348bfd213a23
Script to import – http://gallery.technet.microsoft.com/scriptcenter/9ad93d90-9ca7-4515-b81e-441eda0390c3
Once the script performs the sync (copy/update/delete) of all the Best Bets/Keywords/etc between the two site collections, the Best Bets and Visual Best Bets will work on both site collections.
for other considerations.
Read the article:
FAST Search for SharePoint 2010: Best Bets created in one Site Collection are not reflected in the search results for other Site Collections