As a video tutorial/screencast pioneer and fan, I'm excited to hear from multiple Mac news sources that the next major release of Mac OS X, "Snow Leopard", may include a built-in video recorder. Apple has a storied history of spotting which features will make the transition from esoteric to mainstream acceptance, to such a culturally-impactful degree that it's hard to imagine anything different came before.
Screencasting continues to rise, as Internet video is omnipresent, bandwidth gets phatter (but damn those ISP caps!), and support staff all around the world become increasingly frustrated at trying to reconstruct a non-technical customer's problem through well-meaning words which are subject to extremely fallible misinterpretation. The solution: show things as they are. Having come across this many times in my own professions, anything that makes it easier for customer and company to solve problems together IS BIG WIN. (As opposed to screaming at each other because "You don't get it!")
One feature I hope Apple includes is recording of system audio. The various Mac solutions that can do this use an audio driver (sometimes Soundflower) which "splits" the stream so you can record your mic and computer sounds at the same time. On Windows, this is known as Stereo Mix/What U Hear.
Anyway, learn more at Engadget/Mac Rumors/AppleInsider.
And… even Windows 7 is getting in on the act with their Problem Steps Recorder. Not full video, which will be a, ahem, problem when dealing with UI kinetics, but seems to be a step in the right direction.
Outside of OSes, there are tools like TechSmith's cross-platform Jing which make it easy to record and share videos. I use Jing when I'm in a hurry but want to show off something. But more of these tools need limiters!