The contrast in this photograph is too high for my taste. Although the most prominent characteristic of a silhouette is the absence of shadow detail, I think that the slight shades of grey around the edges of the subject are important too. The contrast here is so high that the highlight on the upper lip and eyebrow are the only reasons for me to believe that this is two people and not a piece of cardboard blocking the light. I like the pose, but the implementation could have been stronger.
This is quite nice. I wish it weren't pushed quite so much (I'm guessing that you enhanced the silhouette in post processing) - I'd prefer to see the teensiest bit of detail on the woman's face. 'course, others would vote you down for that.