There are probably as many, if not more, theme collectors who don't brag, advertise, show-off or whatever else you might call internet exposure. They just collect and don't spend time talking about it. They "quietly" (other than than the frustrated shouts of their losing rivals) buy up any and all items they need/want, adding to an ever growing collection, the magnitude and expanse of which may amaze even the most cynical.
my collecting has always seemed to have some sort of sign wave pattern. i might go a while, winning most (ebay primarily) of what I want, then a rival or two show up and start winning items i want. Occasionally there are surprise winners, those who win something and then I never see them again. those are usually those high end, special items like bat barrels, cut signatures, ridiculously large or specialized patch cards, jersey letters, etc. Some of those prices have shocked me silly.
I see to lose a little more interest each time I lose something major or when a new product like Panini or similar unlicensed junk hits and it's loaded with ugly cards that I feel I must win to remain as complete as possible. Usually those ugly, non-licensed issues are loaded with low print run cards to chase. Why else would anyone buy them otherwise, right?
In the end, I have not actually run up against anyone who I know for sure rivals my specific player collection for completeness. I base this on my hit percentage in the last 10+ years on ebay of not only regular, insert, parallel and oddball car (including 1/1s), but with unique non-card items that I have seldom seen and usually won when I wanted to. I am most proud of that aspect of the collection now that card makers have driven every possible card type into the ground. Those unique oddballs really make a collection shine above the average.
I have befriended a couple formal rivals, both of who have pretty much refocused their collecting so as not to noticeably impact me, one completely disappeared as far as i can tell, a few continue to dwell and cause me some heartburn here and there and 1 has proven to be a consistent thorn in my side on and off for the last 2-4 years or more. i wish that one would disappear...
In the end, i have frequently questioned myself as to what I am doing and what i plan to do with all of my accumulations. My boys are 8 and 10 now and neither has really taken a real interest in baseball or trading cards specifically. I suspect that my collection will either be a burden (it could be a bounty if they handled it properly) on my family to deal with if i go unexpectedly or I will someday soon (soon could be 5-10+ years or more though) begin to dismantle it over time.