IMHO that is one of the main benefit of negative spaces (I didn't know the term but knew the technique): you actually hardly notice that there's "something else" and yet the logos somehow look nice. I'd say they look "soft", without knowing why.

Once you focus too much on "what's inside", it gets a bit confusing because you're seeing conflicting things (like the tree leave that is also people): but it's not a problem because it's not meant for people to really focus on.

And somehow it just works. I find several of these logos really very simple and great.

Now that this has been posted on HN I expect lots of startups to come up with similar logos ; )