I've shown in previous posts that Google takes a long time to clean up their search results and that hijacked websites are still shown in the top 100 results after several days. Here are a couple of graphs that illustrate how many hijacked links (Google results which redirect to a malicious page) are displayed without a warning (red line), and how many links are blocked by Google (blue line) over time (X axis).
A search for "2010 nba draft order" made the top-20 hot trends for the first time on 05/18/2010. I have scanned the first 100 results from 05/19/2010 to 05/27/2010, a total of nine days of results.
Statistics for "2010 nba draft order", 05/19 - 05/27
For this search, the highest number of hijacked links displayed happened on day 2 and day 7. Google started showing warnings only on day 3.
The statistics are even more compelling for other search terms. "american idol top 2" and "american idol top 3" were both popular in mid-May. But the second search significantly more malicious links (up to 31 is the first 100 results), and Google struggled mightily to clean up these search results:
Statistics for "american idol top 2", 05/20 - 05/27
Statistics for "american idol top 3", 05/17 - 05/27
On heavily infected searches (more than 70% of results are malicious), Google took 5 days to do any serious cleanup:
Statistics for "anacostia river", 05/19 - 05/27
More troubling, some searches still contain more than 10% malicious links after 3 weeks:
Statistics for "boondocks season 3 episode 1", 05/18 - 05/23