A social graph is built which includes interactions, sharing activity, and connections between the users of the open Web and can be used to improve ad targeting and content personalization. Sharing activity between two users will affect ads or content that both users will be presented while surfing the Web. This sharing activity includes sending of links, sending of videos, sending of files, cutting and pasting of content, sending text messages, and sending of e-mails. A technique can include a sender sending a first link to at least one recipient. When a first node representative of the sender in social graph is not identified and after receiving the activity information, creating a second node to represent the sender in the social graph.