In Confluence 5.2, labels stopped getting indexed as part of a page. To reproduce:

1. Create a page with a title "foo" and page content with just the word "foo"
2. Add the label "bar" to that page.
3. now search for "bar" from Confluence search.

expected result: the "foo" page will appear in your search results.
actual result: the "foo" page doesn't appear in your search results.