I noticed on a couple querys using uncommon words, Google tends to suggest a query for "dictionary" which isn't what i'm looking for at all. For instance:
http://www.google.com/search?q=fiduciary
I suspect that this problem is due to one or both of the following:
1. a lot of the results tend to be dictionary entries (not so much for this particular query)
2. people are usually looking for a definition when they search for a difficult word, so they're more likely to click on a dictionary result

Out of interest Caleb, what other words did this work for?

Could it not just be that [fiduciary] is semantically similar to [dictionary]?

(I'm not sure how Google do their fuzzy matching but SQL Server's SOUNDEX function can produce some crazy fuzzy search results, so I guess it's possible.)