No information (pertaining to your Facebook content) is being shared from you to GroupOn. Information is being shared from your friends via a Facebook Plugin to you.
GroupOn is using an iFrame that contains a plugin from Facebook called FacePile. So, GroupOn does not have your information. As described later on in "What information is being shared with groupon.com?" and real estate. It is showing you and you alone what other friends are doing in relation to this site. These friends have connected to GroupOn's Facebook application via the Facebook Connect plugin.
This information was posted on Facebook's Blog earlier this year with some merges and summaries made to fit your case.
What information is being shared with groupon.com?
None of your information—your name or profile information, what you like,
who your friends are, what they have
liked, what they recommend—is shared
with the sites you visit with a
plugin. Because they have given
Facebook this "real estate" on their
sites [At a technical level, social plugins work when external websites put an iframe from Facebook.com on their site], they do not receive or interact
with the information that is contained
or transmitted there. Similarly, no
personal information about your
actions is provided to advertisers on
Facebook.com or on the other site.
While these buttons and boxes appear
on other websites, the content
populating them comes directly from
Facebook. The plugins were designed so
that the website you are visiting
receives none of this information.
These plugins should be seen as an
extension of Facebook.
Is this sharing of information something I can disable in facebook?
You should consider the likes and
recommendations you choose to make to
be public information, much like when
you comment or write a review on any
website today or connect with a public
Depending on the connection you made,
you can remove a connection completely
either by going to the "Info" tab of
your profile and editing your "Likes
and Interests," or by returning to the
web page where you liked something and
Likes and Recommendations made on
other sites become publicly available
information, similar to a public
comment on a website. Only click the
Like or Recommend buttons if you want
to share your likes and
In my Facebook Privacy Settings, "Enable instant personalization on
partner websites." is unchecked which
I thought prevented sites like Groupon
from getting my Facebook information.
What am I missing?
Only an exclusive set of
partners—Microsoft Docs.com, Pandora
and Yelp offer personalized
experiences as soon as you visit those
services. These partners have been
given access to public information on
Facebook—such as names, friend lists
and interests and likes—to personalize
your experience when you're logged
into Facebook and visit their sites.
When you first visit any of these
three partner sites while logged into
Facebook, you'll see a blue bar appear
at the top of the site letting you
know that your experience is being
personalized. You can learn more about
it, remove the personalized experience
or click "x" to remove the bar.
For the full run down visit Facebook Blog : Answers to Your Questions on Personalized Web Tools