RapLeaf knows what you did last summer.

The Wall Street Journal continues its exploration of how our privacy is eroding on the Web in new article by Emily Steel — A Web Pioneer Profiles Users by Name. The article profiles the San Francisco startup RapLeaf, which defines its vision as follows.

“We want every person to have a meaningful, personalized experience – whether online or offline. We want you see the right content at the right time, every time. We want you to get better, more personalized service. To achieve this, we help Fortune 2000 companies gain insight into their customers, engage them more meaningfully, and deliver the right message at the right time. We also help consumers understand their online footprint.”

RapLeaf ties email address to profiles with information about people and uses the profiles to target advertisements for clients. The articles shows the information collected for one person, Linda Twombly of Nashua NH, and what some of the coded information means.

Rapleaf does allow you to see the information it has collected about you, but you have to create a RapLeaf account to see it. You might be surprised about how well it knows you. Visit this page to see if your browser has RapLeaf cookies. You can also use it to opt out your email addresses from the RapLeaf system.

To be fair, RapLeaf and other companies are not doing anything illegal and mainly collect information that people choose to make public on the Web. However, their use of cookies does allow them to aggregate and integrate information about individuals and to associate that information with email addresses, Facebook UIDs and dozens of other identifiers. The information can be used to help Web-based systems serve you better — but their idea of serving you better is likely to involve peppering you with targeted ads.