I was thinking the same thing. It's not clear to me though how the search results / feed in sparks is sourced. I assume it's a merging of +1 and shares with some sort of keyword matching, but it seems to show articles in random order and I haven't really figured out what makes it better than a google or twitter search. It seems like they are trying to make it better than a static group because it will include content from any user related to a topic, but it doesn't let me find other people who share my interests to add to my circles and it doesn't show me why something appears in the Spark feed.