While I appreciate the sentiment in Dan's post, as someone who pretty much went from 1980's 35mm SLR + 50/1.8 standard lens, to a 5D2 + four L lenses, I have to say that in my experience, much of the reason for this "collection" behavior is due to knowing what kind of pictures I want to take and knowing that anything less would not be satisfactory. To date, I have not made a purchase wherein I felt like what I bought was more than what I needed, either from a technical or functional perspective. In fact, there are times when I feel like I cheaped out. My purchase of the EF 300/4L IS is one such instance. Don't get me wrong, I enjoy using this lens immensely and I can get very nice shots with it. But long before I bought it, I knew what I really wanted was the 300/2.8. The extra stop, the superior sharpness, the better performance and versatility with the EF Extenders... all of these are things I could fully exploit in my photography.
Another experience I had recently was when I had the opportunity to try out the EF 50/1.4, a lens I do not particularly covet. And when I did, my impressions were confirmed. The soft, dreamlike performance from f/1.4 - f/2.8 obviates the need for me to own such a lens for the wide aperture.
I guess the bottom line is that for many "collectors" out there, a big motivation for the collecting is knowing precisely what they need for taking the shots they want, and how they intend to use it. That's not to say there aren't people who collect just for the sake of being able to say they own a particular exotic lens, but Yakim certainly does not come across as such. I am quite sure that he would have absolutely no problem finding ways of maximizing his usage of the TS-E 17/4L!