Videoing an event that features a speaker or authority on a subject has a number of advantages:
Later playback to those who missed the event
posterity
A souvinir gift to those who attendend. [The video is given out later, say 2 months later and has the effect of re-living the event - an endorsment of the event.]
A record of important points and issues pertinent to the event.
To new staff.
Record of the event for subsidiaries and sister corporates.