No argument with your clue for Mr. Bean, but Orson Bean (you saw him as a young man in "Anatomy of a Murder" and much older in "Being John Malkovich") also fits the category. A little rewording would avoid the ambiguity.
There's a big cognitive difference between recall and recognition. I'd be willing to bet that Dickinson is a name a lot of folks would recognize but I'm not at all surprised only 1 in 3 recalled it (especially as clued).
What is unique about williamson?? quite a normal name. (or do you mean it would be the only williamson on the list? well in that cause you left out about a 1000 other names ending in -son)
It is interesting to see which people can recall though.