"Yahoo (YHOO +0.3%) is building an interest graph--a map of what users are interested in that the company can use to personalize their content," writes Fast Company's Sarah Kessler, after surveying the Web giant's recent acquisitions of Summly, Snip.it, Jybe, and 2 other startups. Kessler sees the acquisitions, which coincide with the launch of a revamped home page featuring a personalized news stream, as part of an effort to create a positive feedback loop between greater engagement and personalization.