I've not yet been able to get a video to play on the iPhone, and I'm assuming it has something to do with the if statement encapsulating the PlayMovie command. My iPhoneStreamingAssets folder is next to the Assets folder in the main file structure.
Here is the code I'm using:
if(GUI.Button (Rect ( (Screen.width*( (button_locX+5)/10)) - (button_sizeX / 2), (Screen.height*((button_locY+move+.2)/10)), 80, 35), "Preview") )
iPhoneUtils.PlayMovie("jump.mov", Color.black, iPhoneMovieControlMode.CancelOnTouch);
If you're using Unity 3, keep this in mind (pasted from the beta changelog)
iPhone: iPhoneStreamingAssets is renamed to StreamingAssets and is now located under the Assets folder (visible from within the Editor).
Also, I would use .m4v, not .mov :)
to answer your question, first I must ask what version of unity iphone are you using? is it pro or is it basic.
because it seems that there is nothing wrong with your code so I assume that your unity iphone is the basic version which unfortunately doesn't allow you to play video.
I hope that helped