I try to use SO (or any other SE site) search to find the post with specific URL, e.g. I try to search for http://www.joelonsoftware.com/items/2007/10/26.html on SO.
I get no search results, while there are quite a few when I use Google, e.g. What's the best resource for learning about Evidence-based Scheduling?
Using URLs in search does make sense when we look for similar threads on the site or when we're looking for specific question/answer where we know the link was used.