You have Mark, but I think David's point is made too...
He just shoots you.
Ron (and yes, I know the 19 - 20 - 21 foot rule. Apparently, so does David...)
LOL, uh yeah. Gun trumps knife unless knife trumps gun.
But, seriously, no, that wasn't my point. My whole point is that people are using a knife for training and they're being very complacent about it. You think anyone here would be complacent if someone used a live, sharpened katana and tried some "flowing" drills? How about substituting a live knife for those same flowing drills? The point is that the tanto isn't just some wooden unsharpened tool used to help "flow". It's supposed to be a safe version of the real thing to help assess your principles in motion and how they work. You move like you train. You react like you train. If you burn in hundreds of hours of complacent training with the tanto now, what do you expect will happen when you encounter the real thing?
Relook at that video and see the cuts that were made on a body. See the guts hanging out? You want to be complacent in your training about that? How about the 1/2" down artery running alongside the inner arm that only takes a slight cut to sever? 30 seconds without help and you are done. Period. End of life. Or a cut to the neck and sever the artery there. 5 seconds. Anyone think they can end the fight, call 911, and survive until the ambulance arrives with those kinds of cuts?
And that doesn't begin to cover the cuts/stabs/etc that are life enders, no saves. A tanto isn't just some tool to add to training to induce "stress", add "flow", or play with. Whenever someone picks up a tanto, the thought should be one foot razor blade designed to kill -- for both tori and uke. I dunno about other people, but I'd rather not have complacency in my training. My life might depend on my training. Ichi go ichi e. Once time, one meeting. That's particularly important in knife work.
Then again, I don't think I'm doing aikido yet. I'm more aikibudo right now, so YMMV.