Came across this post. CRM 2011 Rollup 10 gives option to enable or disable records limit for Quick Find to improve performance. You can find this in System Settings dialog in General tab.
The record limit is 10000. If quick find found more than 10000 records, it will prompt the message below:
The Quick Find limit is exceeded. Narrow your search by entering a longer query, or use Advanced Find.
Read more here.
Cheers – Sy