PS. Evidence is NOT only anecdotal.
Propolis has tremendous anti-infection qualities, I just came across an article that at the Univ of Minnesota they are studying it against AIDS and are getting promising results.
http://www1.umn.edu/umnnews/Feature_Stories/Propolis_an_ancient_remedy_may_fight_AIDS.html
I was given that article last year when I worked at the U of M and I was previously aware of this study and look forward to their results. Note that it is being studied for promising properties - not the same thing as an endorsement of propolis in general. For one thing, they are going to have a heck of a time developing a reagent grade propolis material because of the extreme degree of variability in basic resource use by the bees.
BTW, I use this exact article in some sales and promotional materials I keep on hand.