I have 100%. Once I got into the knife hobby I stumbled on Jim Skelton and gktii. Long story short, i've owned a Curtiss F3, Greg Lightfoot Full Contact Fighter, Hoback Kwaiback Midtech, and have a Direware on the way. Reason was because, I watch these videos at work (very relaxed work place) and while I glimpse at the screen, a particular knife will catch my eye while watching one of their videos.
Jim Skelton alone has been the cause of me spending a lot of money on knives, and so far every one I have bought off of his assesment has been stellar and pretty much what he described, even if I didnt hold onto it long. I dont use Youtube so much as a "what should I buy next", more so a, to see whats out there and to be able to see high quality video of it. I could go on AZcustomknives and look at pictures, but I dont connect with pictures as much as I do with a 20 min long video of a knife.
Typically, if I see a knife on one of those channels and it peaks my interest, ill do futher research on the knife, maker, etc... Then I will make my decision. But I can safetly say that Youtube has caused me to purchase knives.