I do think this is BIG but...I also don't think it's any surprise. It's been pretty obvious that this is the way that the internet was evolving.
Considering that one of the fundamental essences of the internet is that it's just a way of connecting 2 or more humans, it only makes sense that anything people can do together (intellectually anyway) should be able to be done on the internet.
This obviously includes teaching. After all, all teaching is is the human equivalent of 'data transfer', right? One of the biggest limitations has been the size of the screens that people have in their computer set-ups and also the strength of their video connections.
I'm thinking especially of how improvements in these two factors (screen size and band width) relate to teaching things like dancing. This sales pages mentions somebody using Google HelpOuts to teach Yoga but, in my view, that's somewhat similar.
But I'll guarantee you that there's going to be gold rush of people getting into using this kind of technology to teach and consult. For one thing, I think that if a person could really learn this....it's going to creat a boatload of opportunity for language teachers (especially when you incorporate the multiple participant features of Google Hangouts).
This kind of technology is going to radically effect the 'seminar' business too. I suspect that to really 'max' it out, a person will need to incorporate Google+ (and various Google+ "Pages"), and know a little bit about SEO.
And probably, in using HelpOuts to market, it would also be a good idea to incorporate YouTube and some astute video SEO too.
But anyway you slice it, I think the opportunities presented by Goodle HelpOuts, and the way of thinking that goes along with it, are awesome. I've got this product on my 'buy soon' list.