Ben,
I could not agree more with you. One of my pals on
flickr once compared that 'collector's itch' to an addiction, and I guess he's right. At any rate, it's a prestige thing, and a surrogate thing. In the words of German philosopher Erich Fromm, we're basically trying to replace
being with
having through this constant craving for more and more and still more...
One caveat though; I think by buying into different camera systems you can also--by trial and error, as it were--
learn a lot, namely, what type of shooter you are and where your individual preferences and strengths might lie. In other words, how do you know what you're really looking for unless you have the opportunity to give things a try?
Come to think of it, it was sheer GAS, this typical 'must-have' itch, that led me into buying the handful of cameras that I really
love working with, e. g., the Kiev 4A (a Ukrainian Contax II rangefinder copy) or, quite recently, the Pentacon Six. When the latter arrived in the mail, a couple of weeks ago, and I unpacked it and opened the viewfinder, I knew immediately,
this it it...! 
(I find myself sort of 'moving back in time' anyway, preferring solid mechanically-operated cameras over gear stuffed with electronic gimmicks, but that's another issue.)
Then came the hard part, that is, parting from some good cameras which I had that collector's pride of owning yet never really got the hang of. And--hooray!--I actually made it, sold off my minty Yashica Electro 35 GX rangefinder and my medium format Pentax 645 which I knew I would hardly ever use again, and was rewarded by a completely new sense of pride, the pride of being
reasonable, for a change.
And it is
some relief to rid yourself of things you don't need (and even get back the money you invested).
So I've now made a vow to myself (and my wife), saying...
...(1) for each of my five favorite cameras I am allowed one--and only one--backup or organ donor
...(2) for each new camera I acquire another one must go
...(3) every camera I do not use within one year will have to be sold.
I know this might seem pretty childish to some of you, but I guess camera junkies like me must simply learn to discipline themselves, some way or other...
Michael