Jon Kleinberg is part of Discover Magazine's list of "The 50 Most Important, Influential, and Promising People in Science", which is featured in its December 2008 issue.

See:
http://discovermagazine.com/2008/dec/19-the-50-most-important-influential-and-promising-people-in-science

And
http://discovermagazine.com/2008/dec/20-best-brains-under-40/article_view?b_start:int=2&-C=