Re: To do or not do that is the question... (bringing food in to your dojo)
We occasionally do socials after seminars. We have a seminar coming up in may where we will order pizza or Chinese food after the Friday night class and have a social event (Sat. night being the mandatory 'going out for sushi' event).
As for friends: it's pretty hard to train with people for ten years..someone who obviously has a similar, yet unique, interest as you and not become friends. Now as far as dojo relationships go...that is a pretty big slippery slope. They usually end with one of the two people leaving the dojo...or marriage.