Comment 4 for bug 392266

A recent excerpt from Stuart Bishop on this topic:

"""
The reason we currently have https://bugs.launchpad.net/ubuntu instead
of http://bugs.ubuntu.com is authentication. We always wanted product
specific domains, defaulting to foo.launchpad.net and allowing people
to use their own domains. Unfortunately, OpenID didn't exist at that
time and we didn't want to invent it ourselves.

...

The real solution depends on Launchpad becoming an OpenID consumer. We
can then stop requiring a cookie to be shared across all the domains.
This gives us Launchpad over HTTP for a big perceived speedup, fewer
security concerns with session cookies, and the ability to host 3rd
party domains.
"""

We do have plans to become an OpenID consumer.