The Viddler WordPress plugin promises to “Enrich your site’s commenting experience by enabling video comments….” Users can record direcly from a web cam or choose a video they’ve previously uploaded to Viddler.com.
Viddler evangelist Colin Devroe has it on his site, where I can see it requires would-be commenters have a Viddler account. That last bit is too bad. I like Viddler, but I can’t force my readers to like it and get accounts as a prerequisite to commenting.