From: Jaimie Vandenbergh on
I think deKay was peeved about this one. Just came across the solution
over at OSXhints -

http://www.macosxhints.com/article.php?story=20080629181121863

which says to use

defaults write com.apple.screencapture disable-shadow -bool true

then

killall SystemUIServer

(or logout etc) to initialise it.

Cheers - Jaimie
--
It is better, of course, to know useless things than to know nothing.
- Lucius Annaeus Seneca, 'Epistles'