Aqua-Soft Forumshey people just posting this for a friend who wanted to know if he could use his DVcam to take the place of isight.
Using DVcam instead of webcam isight
using what? for ichat? for imovie? thanks for being so specific.
if so there are ways for both. to use it w/ ichat requires 3rd party software but it is possible
I am gonna go with a web cam option 
In all honesty it would also depend on the DV Camera he/she is using.
Not all DV Cameras have a "Monitoring" facility where you can monitor what your viewing for more than 10mins as they go into power saving mode and switch off unless of course your recording or playing back.
Also how the camera is connected would determine what 3rd Party Plugins you would need.
One of the The Best I have found so far is a Freeware Program Called MacCam. if it works with DV cams I do not know, but if your friend has a Compact Digi Photo Camera capable of taking video then some have a PC Web Cam facility (fujis do)
iSights are very nice but I do think they are somewhat overrated.