As it is outlined in the email:
1. Demographic portions of your data (such as zip code, gender, or industry) and usage patterns may be shared with our trusted partners who deliver advertising to you on our behalf. Consistent with our current policy, personally identifiable information (e.g. your name, address, phone number, email) will not be shared with third parties for advertising purposes without your consent; and
2. The advertising networks who deliver ads on Plaxo may use their own cookies to collect information about a user's activities across their entire network of Websites.
It is a slippery slope when companies start "sharing users information".
Optimising Digital Marketing Campaigns with Search, Social and Analytics
At SES London (9-11 Feb) you'll get an overview of the latest tools, tips, and tactics in Paid, Owned, Earned, Integrated Media and Business Intelligence to streamline your marketing campaigns in 2015. Register by 31 October to take advantage of Early Bird Rates.