I wrote the W3C logfile draft, if you look at the archives you will note it
has two sisters, a session ID draft and a logfile exchange scheme
for demographic data.
The drafts were written after a conference on demographic data for
the explicit purpose of facilitating limited exchange of information
to facillitate payment for content.
The reason why I was concerned is that without such schemes sites
are forced to use cache busting techniques to increas their income,
they cannot know how many exposures they get through a cache
so they bust it. To do otherwise costs them income - hard to justify
if like all online content you are loosing money.
I'm fully aware of the privacy issues etc and I believe that in the long
term P3 will be a big advance for everyone. The problem I had to deal
with was very short term however. - it still took almost 2 years for
this to reach product, the development of the Web moves at a glacial
pace.
If Microsoft are uploading a field I would hope it would be the
statistically unique session Id I describe. This is unique for each
site but does not need stupid cookies to track a person through
a site. The cookies are cryptographically formed making it
impossible to correlate them across site except by exporting
them through a URL of some sort.
Phill