I posted this on the "A Scandal in Belgravia" page but I think it's better here!

I noticed many parallels between Sherlock and Irene. Some of their similar actions foreshadow the events to come later in the episode.
 
My list:

1. Sherlock looks through her photographs; she looks through his.
HOWEVER, he only looks through her photos once and she scrolls back to the first photo of him. This difference illusrates her interest in him.

2. At one point in the episode, both Irene and Sherlock are naked.

3. Both change wardrobe, or at least try to, struggle with a costume, and say the word "battle."

4. Both "need a splash of color." Sherlock gets punched and bleeds; Irene wears blood red lipstick.

5. Both play "the game." Sherlock devotes himself to the demanding and distracting qualities of the game and Irene does the same, except from the troublemaking side.

6. Some superficial similarities: They have similar appearances, vocabularies, taste in expensice wardrobe, and the same blank stare.

Those are the parallels that I found; does anyone see any others?