If we would have more than 600 people in a buddy list, it's kind of
cumbersome to scroll through it, and it's also expensive to render
it (short of doing progressive rendering, which adds a lot of
complexity).
So, as a short term measure, we filter out offline users whenever the
list would exceed 600 users. Note that if you are doing a search that
narrows to fewer 600 users, the offline users will appear again.
Steve Howell