Re: YouTube - good or bad for aikido?
I have found u-tube extremely helpful. Always look for a video of the previous class's techniques so I can mentally review and recall what it looks like. Created a play list of the techniques on my upcoming test so I can work on linking technique names to their movements. And one very generous utube member created some videos just for me on Ukemi for the larger person.
As with anything it is important to use good judgment and common sense. And at the end of the day it is what goes on in your own dojo that matters most.