Nudge does use your contact data to contribute to the overall Nudge database, but only public data is shared with other Nudge users. For example a twitter ID would be shared, but not an email address. As a user you also benefit as your own network will be updated with public data from other users. We never share private data or notes you take on your contacts. We never share any of your data outside of the Nudge user base. The other data we share is your Network Health Score, and that is only seen by other users. If you choose to collaborate with other Nudge users, you can share the relationship strength you have with your network with your collaborators.