Normally, in most case, it can't. But maybe some camera have value-added features to enable it to be a webcam, so you should check the manual first.
There're actually a few software to turn DV (not the type of camera you refer to I guess) to a webcam. I've tried DVdriver myself before, it worked fine but need to re-connect every min as I just used the trial version. There should be an illegal hack somewhere I guess. Webcam is cheap enough and DV is bully enough, so I just buy a cheap webcam to cut the trouble.