I noticed this as well and I like it, it's sexy without being too much. It fits the assymetrical trend well. But I like it when it's done without cleavage, with cleavage it's a bit too versace for me.
^ I totally agree. There's something so sexy about this trend. I especially love it when its directly on the side and you really only see the leg as the woman walks.
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You need to move fashion forward when there's a reason to move fashion forward - Tom Ford
Note how most of the looks posted are the longer hemline - it's designers keeping the length sexy.
It looks great.
If we're talking about slits, I hope you'll excuse me mentioning slits up the back of clothes also, starting with Balenciaga and Bouchra Jarrar couture for winter, and then to Proenza Schouler and Isaac Mizhari (majorly) for spring.
Screencapped by me from the Balenciaga A/W 10-11, Bouchra Jararr Couture A/W 10-11, Proenza Schouler S/S 11 and Isaac Mizrahi S/S 11 shows
Seems to be the trend this season and I too noticed it in many shows and it actually works. Showing skin but not too much. Love how the dresses move as the models walk..