This practise is on the rise. And you will notice there are more white stormtroopers on ebay than before this is due too this tecnique and 'poon troopers'.....
I toyed with bleaching my childhood figures earlier this year but changed my mind. They are what they are because I had so much fun with them when I was a kid, bleaching them back to tipex white would take away that history. Also, no one really knows what the long term effects of peroxide are on the plastic.
Tried it on a 12 inch Stormy years ago with peroxide and it did work well, but before too long it went yellow again. Be careful if you do this. There was a thread not all that long ago where someone destroyed an Imperial Shuttle (it melted ).