Why "flower petal" lenshoods?
 

Are they better? or just cheaper? Or is is a style/fashion thing that they are appearing so much on camcorders now?

I would have thought that the rectangular shape would be more efficient at keeping flare off the lens.

Re: Why "flower petal" lenshoods?
 

Just guessing here, the lens hoods are always situated with the cut openings / slots in the corners, the sensors are a rectangular and the slots keep the hood from showing or darkening the corners of the shot. Also cuts down on weight and provides impact protection.

Re: Why "flower petal" lenshoods?
 

They just look cooler... <wink>...

Actually Don hit the nail on the head for the most part - you'll notice that typically the "top" and "bottom" petals are longer/wider to give better coverage to the longer edge of the image, and as Don stated, the corners scale back, to avoid the hood getting into the picture. this geometry allows the hood to be smaller than a full box shaped one.

Re: Why "flower petal" lenshoods?
 

I've noticed that the 3x Wide angle XL lens has the flower hood where as no other Canon XL lenses I've seen have had one and based off it's shape I assumed it was to avoid vignette on wide angle lenses.