A few reviewers have been very influential at times, but like a lot of people on here, I do my own research; Youtube is a big part of that, but it's never been the only source, as far as I can remember.
The Apostle P's review of the Benchmade 761, however, stopped me dead in my tracks, seconds before handing my money to the metaphorical cashier. I was very impressed by the 761's sleek appearance, and even the tip-down clip didn't bother me. I couldn't think of anything that might dissuade me from buying it, but that was just a failure of imagination on my part. AP's review pointed out some serious faults, like a detent so weak the blade would fall open with the slightest prompting, and a lockbar that was dangerously thin and lacking in tension -- which was also related to the weak detent. I was going to order it later that day, and was comparing shipping rates when the video was uploaded.
I've since seen another review on the 761, this time by Will Moon, and this time very positive, specifically addressing the potential problems brought up by AP. I know Will Moon has had problems well-documented on Bladeforums, but regardless what you think of his questionable business dealings, he's an excellent knife-maker, and he knows his stuff. Whether or not AP just happened to get the one bad knife in a thousand, or the one bad knife in ten, unfortunately, those criticisms decided the issue, for me. It takes more than one positive Youtube review to sell a knife, but one negative Youtube review can definitely make me reconsider. With the 761, however, my decision not to buy was also related to my own suspicions about problems with Benchmade's quality control.