With the dark tone of the series and how everyone is essentially a "Dark" magical girl already, I fully expected the soul gem to shatter in the first place actually.
Why did Madoka throw Sayaka's Soul Gem on the road?
She didn't realize the real effect it would have on Sayaka; she thought it would just keep Sayaka from transforming into a magical girl and thus prevent Sayaka and Kyouko from fighting to the death as magical girls.
Homu!!*run**whooshー*A···When it comes to some things, making a mistake means the end, Madoka...Episode 6*crack**vroooom···*Magical Nekomimi
Homu ☆ MagiThere!!*snag*Sayaka-chan, I'm sorry!I am so immensely cool now...*pant* *pant* *wheeze*
etcOne way is to be bold and make a mistake...Want a Pockyyy? "Irregulaaar~"Ho···Homu···