Tags as virtual venues
I can't stress this enough... if you are holding an event, or thinking about holding an event, or even thinking you may want to think about holding an event, decide what tag you are going to use as soon as possible.
A large part of your event's impact will come from the collective writing, images and videos by the people who attended. The only effective way of tying all this material together after the event is via the event tag.
It's easy to forget, but I'd go as far as saying that the tag is almost as important as the venue. In fact, in a sense, the tag becomes the virtual venue for the event's digital legacy.