One problem that arises when something gets trendy the way using video for internet marketing is these days is that a lot of people who don't know how to do it right jump on the bandwagon. I have a big gripe about what some people are doing with video these days.
Before I continue, I should point out that I think video is a great tool for marketing. It just has to be used well. And I don't mean that the production quality has to be great or anything like that -- it just has to add value over what could have been done without video.
The problem I'm seeing lately is that some people will put a video on their "squeeze page" (the page where they try to get you to join their mailing list), but the video won't contain any substance. Video is great when it's entertaining or informative, but when it's just a talking head spending 2 or 3 minutes to say "hi, my name's Joe, and if you join my mailing list, I'll reveal the holy grail of internet marketing", I feel cheated.
The video wasn't interesting in the least. It didn't contain any useful information (so why would I believe that the content I'm being asked to sign up for would be any better?) It didn't communicate anything that couldn't have been communicated faster using text.
I've read predictions recently that the boom in online video is going to bring the internet to it's knees in coming years because nobody wants to pay to upgrade the internet's capacity enough to carry it. True or not, these empty videos are a waste of time and bandwidth.
Unlike with a text webpage, I can't scan a video to see whether there's anything in it worth spending the time to get -- I have to watch the whole thing to find out. In my mind, when someone posts a video, because of the time commitment they're asking of me, they are implicitly promising that there's value in the video itself. If that promise is broken, the likelihood of my subscribing to more from them drops.
If you're going to use video, make it entertaining and/or make sure there's enough in it that I can use (even if I don't subscribe to your mailing list) to justify the time I spend watching it. Video should help establish your credibility, not call it into question.