From the CML list this warning about Yahoo Groups,
If you belong to ANY Yahoo Groups, be aware that Yahoo is now using
something they call "Web Beacons" to track every member of every Yahoo
group. Web Beacons are similar to cookies, but allows Yahoo to record
every website and every group you visit, even when you're not connected
to Yahoo.

Look at their updated privacy statement at
http://privacy.yahoo.com/privacy

About half-way down the page, in the section on cookies, you will see a
link that says WEB BEACONS. Click on the phrase "Web Beacons." On the
page that opens, find a paragraph entitled "Outside the Yahoo Network."
In that section find a little "Click Here to Opt Out" link that will
let you opt out of their snooping. Be careful! NOT to click on the
next button shown. It is an "Opt Back In" button that, if clicked, will
UNDO the opt out.

Note that Yahoo's invasion of your privacy– and your ability to get
out of it – is NOT user specific. It is MACHINE specific. That means
you will have to go through this same process on every computer (and
browser) you use.
From Yahoo
Web pages may contain an electronic file called a web beacon, that allows a web
site to
count users who have visited that page or to access certain cookies. Yahoo! uses
web
beacons in the following ways:

From the Yahoo! Network explanation

Yahoo! uses web beacons within the Yahoo! network of web sites in order to count
users
and to recognize users by accessing Yahoo! cookies.
Being able to access Yahoo! cookies allows us to personalize your experience
when you
visit Yahoo! web sites that are located both on and off of the yahoo.com domain.
For
example, Yahoo! GeoCities pages are mostly located on the geocities.com domain.
Outside the Yahoo! Network

Yahoo! uses web beacons to conduct research on behalf of certain partners on
their web
sites and also for auditing purposes.
Information recorded through these web beacons is used to report aggregate
information
about Yahoo! users to our partners. This aggregate information may include
demographic
and usage information. No personally identifiable information about you is
shared with
partners from this research.
When conducting research Yahoo!'s practice is to require our partners to
disclose the
presence of these web beacons on their pages in their privacy policies and state
what
choices are available to users regarding the collection and use of this
information. You
may choose to opt-out of Yahoo! using this information for this research. Please
click here
to opt-out.
Note: This opt-out applies to a specific browser rather than a specific user.
Therefore you
will have to opt-out separately from each computer or browser that you use.

If you have to leave the group because of this then I understand.
I really am against this policy.
Mark Forman
Group Founder