sorry for my delayed response... duty calls and all that. as for traffic fluctuations, the thing i've noticed when it comes to traffic has to do with the subject and the title of the post... even more than my posting frequency.
another time i see more traffic is if i link out to some of the other
SEO/SMO gurus. they will usually drop by and comment or link to my post from their blog. but i don't doubt frequency helps as well (some days are definitely better than others).
as for the other people, we do have blog contributors to WPN, but i'm normally the only one doing updates on the WPN blog. sometimes other authors post there, but it's normally just me.