Yahoo traffic more 'stable' than google and msn?

Yahoo visitors per day (to some site) always same, unlike google and msn..?

[Drreggae]

On one of our sites, we get google traffic via adwords,
and yahoo and msn traffic for free, as apparently ink.
likes the site..

Now our msn traffic slowly dropped away to 0 over the last few weeks, but that's a side-issue...

During many months now, we observed our google as well as
our msn traffic to this site, drop around 33% in weekend days, and holidays (sometimes even bigger drops)..

However, yahoo search sends roughly the same amount of
traffic each and every day, no matter if it's weekend,
holiday, or weekday...

Has anyone else noticed things like this? or have a theory or possible explanation about it?