Ugh...my local ISSA chapter (one of the biggest and most active in the country) used to entice Sans into coming to our town...they come to a city close by regularly, cuz it's pretty big, but our city is a bit smaller and less of a draw. Anyway, leveraging the ISSA name, we'd get 20% discounts. Throw in my employer paying 50%, and that is quite a bargain. :D
You always get a few know-it-alls in any class, and while I can appreciate the active discussion of diverging points of view, when I pay that much for a class, it's time to SHUT YOUR PIE HOLE! Definitely a con, but one that can (usually) be worked around. In my GSEC class we had a gray-hat (I think he was a blackie in disguise, personally) who did this...and finally got shut down by the professor.