I was just exploring Alberta’s VCAlberta.ca website, and ran across a nice collection of Frequently Asked Questions. They are more creative and useful than the usual run of the mill FAQs out there, including the one on my site!
I quote Question #3:
Question: Do I spell it: videoconferencing or video conferencing or video-conferencing?
Answer: All three are commonly used and the use tends to follow what a localized community has decided is the right way. Videoconference as one word is the most common usage in Alberta and in fact the proper spelling. The oxford dictionary, among many other dictionaries, refers to videoconferencing as one word: Oxford Dictionary
Now you know!