I think you get a little bit of topic in the thread "xtreme sport type shots with lots of motion". So here in this thread, a new question:

I tried out som action shots, and here is deal: I would like to shoot fast action @ 25f (living in the PAL world). My choice is a fast shutter, @ 2000 or something. In the picture, my daughter throw a stone, background is blue skies, and if I could freeze the whole sequense, the motion of the stone would end up in a dotted line!

And here comes the maybe stupid silly question: Is thera any work around? Could shout at fast shutter/25f without retain the "dotted stone line". Or is this a artifact created by the compression (HDV)? Or is it like my impression, fast action with high speed shutter is better in interlaced?

The answer is fairly simple. You're taking 25 frames per second but each frame only records 1/2000th of a second. So the first frame records 0.5mSecs of the stones motion, then nothing is recorded of its motion for 39.5mSecs and then another 0.5mSecs of its motion etc.
Result, a dotted line.
That's why ideally the shutter speed is as low as possible, around 1/40th at 25fps for video or 1/60th (I think, for film, the camera needs time to move the film).

Even at 50i you'll still get a dotted line, less so than at 25p though.

Of course at the lower shutter speeds you get motion blur, the object moves with the frame. That creates a problem for slo mo which is why sports stuff is shot with a faster shutter speeds but it makes the action look stroby. The ideal is to use a very fast frame rate but such cameras get expensive.