I think you notice it more because you are looking for it more. Before I started doing 3k peaks, I would see something like Chandler/Sable or Mullen and not even read the report because I didn't know where the mountains even were or care who was doing them. Now you recognize the same characters over and over again here on this message board.
There certainly is an active group of 3k peakbaggers, but it is not as big as you might think. I see the same names in the registers time and time again. I have found about 75 registers now, and these are the names I commonly recognize (in no particular order):
Neighbor Dave, Onestep, MHRSebago, Pig Pen, Marc Howes, Karl Barry and JS from Keds, Keith and Julie, Bigmoose, Pat and Audrey, J&J, Nate, NH_Mtn_Hiker, Spongebob, Mick Dunn, MJ, Gamehiker, Ed Hawkins, Doc Ross, and Michael...
Not to mention all the finishers such as DennisC, DMS, Eugene Daniell III, JimC, Narciso Torres, Glen Houle, Ginger "Snap" Lang, RoySwkr, John Swanson, John McHugh, JR Stockwell, and Anne Gwynne... many of which are also active here.
I am honored to add my name to these lists. Some appear to only be working on the NHHH list. Some of us are working on the lists more fervently than others, but I'm sure with all of the information out there on the 'net, most will eventually finish if they want to. I don't know about some of the others, but bushwhacking is very enjoyable for me - I was telling my friend Dave on Sunday about the feeling of pride and satisfaction I get when I find a cannister and then navigate my way out of the woods in one piece. To me it is far more challenging and rewarding than just regular peakbagging. So to answer your question: no, I don't think it is trendy. There is just a small group of "us" out of the huge hiking community, and many of us are active on these message boards for obvious reasons - the free exchange of information.
I would disagree that notoriety has much to do with it. I found 2 jars on the Captain. The only names in there in the last 2 years (I think) were Roy Schweiker, BigMoose, Arm and Frodo, NH_Mtn_Hiker, Keith and Julie, JR Stockwell, Karl and Motabobo, and Neighbor Dave. 9 groups of people in 2 years isn't much... On West Field and Whitewall, we were the 3rd party to reach the cannisters this year each time. Scar Ridge and Vose Spur had tons more names in the registers - the NEHH is far more popular than the 3K list.