Update and Clarification: Expedia says the Groupon-Expedia agreement stipulates that Groupon shares "email addresses and basic information about subscriber purchases" with Expedia.
And the updated Groupon privacy policy states that it only shares Contact and Transaction Information with business partners.
Groupon defines Contact Information as: "...name, postal addresses, email addresses, social media website user account names, telephone numbers, or other addresses at which you receive communications from or on behalf of Groupon."
Groupon defines Transaction Information as pertaining to "how you interact with Groupon, such as the GROUPONs you view, purchase and redeem; other information about how you use our Sites, email, other communications, and applications; and how you interact with Groupon merchants, business partners, and service providers."
Groupon does not share with Expedia other Personal Information that Groupon collects, including Relationship, Financial and Mobile Location Information, Expedia says.
Expedia explains:

As part of our agreement, Groupon shares with Expedia the email address and basic information about purchases by subscribers who signed up for Groupon Getaways with Expedia. In other words, Groupon merely reports to Expedia basic purchase information – customer’s email address and basic information about the deal purchased -- related to the cobranded Groupon-Expedia Program.
Groupon does not share information with Expedia about any Groupon customers who haven’t signed up for the cobranded Groupon-Expedia offering.

Information provided to Expedia today is in accordance with our revenue-sharing arrangement. Expedia does not currently use this data in any other way; if that changes, we will only use it pursuant to our privacy policy.
Part of the confusion about what personal data Groupon shares -- or doesn't share -- with business partners might be attributed to a Groupon email, Updates to Privacy Statement and Terms of Use, which Groupon has been sending to subscribers this week.
Part of the email states:

You may know that we've started working with partners to offer Groupon users new deal categories – for example, travel deals with Expedia. Our new privacy statement explains that we may share your personal information with these partners if you subscribe to special communications or buy deals in these new deal categories. See Section 4 of the Privacy Statement.
Although Groupon defines the personal information it gathers as Contact, Relationship, Transaction, Financial and Mobile Location Information, Section 4 indeed states that personal information-sharing with business partners is limited to Contact and Transaction Information.
The original post follows:
Groupon revamped its privacy policy and it will provide a treasure trove of personal information for Expedia.
In an email to subscribers, Groupon announced that it had widened its definition of the personal information it may share with merchants and business partners to include "interests and habits," according to The Chicago Tribune.
The email explained that if consumers sign up for Groupon Getaways with Expedia, the pending travel offering from Groupon and Expedia, then Groupon will share users' personal information with Expedia, the story says.
To be clear, the personal information under discussion is not merely aggregated information about consumer behavior, which Groupon also collects and shares, but personal data including transaction, relationship, contact, financial account and mobile location information, according to Groupon's privacy policy.
For example, here's how Groupon defines the Relationship Information it collects:

Relationship Information that helps us to understand who you are and what types of offers you might like. This includes lifestyle information; location information related to your state/province, city, or neighborhood; areas of interest, the types of deals that interest you, information collected from social media interactions (such as via Facebook Connect); demographic information (e.g., birth date, age, gender); information about persons for whom you have purchased deal vouchers (“GROUPONs”) as gifts or who have bought GROUPONs as gifts for you; and information about friends who refer you or who you have referred.
Users of Groupon's mobile apps will see their location data accessed and shared even when they are no longer connected to the Groupon website or Groupon apps, Groupon says.
Expedia and other Groupon business partners likely will be able to use the burst of personal data to better target their offers and for advertising purposes.
When you consider that Groupon is expanding at a frenetic pace on a global basis, then you'll realize how valuable this personal and aggregated data might be for Expedia. After all, a portion, at least, of Groupon's customer base may have never booked a flight on Expedia.
And, once Groupon shares users' personal information with third parties, it says it can't control what the partner site does with that data.
"We encourage Groupon merchants and business partners to adopt and post privacy policies," Groupon states. "However, the use of your Personal Information by such parties is governed by the privacy policies of such parties and is not subject to our control."
Expedia.com's privacy policy explains that it may share consumers' personal information with other Expedia Inc. companies, including TripAdvisor, Hotwire and Expedia UK, for example, and suppliers when they need it to complete a transaction.
In addition to personal information, Groupon will share aggregated information about consumer behavior with Expedia, a move that could round out the information Expedia Media Solutions already collects for its PassportAds program.
Expedia didn't immediately respond to a request for comment.
Groupon has a number of ways, including management of email settings, for users to control the scope of the promotions they may receive because of the collection of personal information.
Consumers also can opt out of behavioral advertising here.
Of course, if you really don't like Groupon's privacy policies, the group buying site suggests you don't register for the site or subscribe to its emails.