I know you're talking about more general issues, but since you posted
this particular example, you might be interested in this conversation:
http://n01se.net/chouser/clojure-log/2008-04-11.html
Which includes this snippet from Rich: (some #{1} [1 2 3])
That returns true because an item in the set (1) is in the collection [1 2 3].
--Chouser