• by Joe Mandese  @mp_joemandese, Yesterday

This column begins with a conversation I had with Horizon Media's Bill Koenigsberg one month ago -- about a week before news broke that WPP was rebranding GroupM as "WPP Media."

"It's a nice story about our continued commitment to our space, our people, and how our clients feel about the environment," Koenigsberg said, pitching me on a story about a real estate deal Horizon struck extending its lease at 75 Varick Street in New York City for another 17 years.

The location had already been Horizon's worldwide headquarter for 15 years, and the commitment did say something to me, both professionally and personally.

Professionally, it said something about the durability of Horizon's culture and the fact that Koenigsberg had tied it so much to a physical presence. In an age of ephemeral, digital, fungible media, Koenigsberg can still see himself sitting in his corner office, overlooking the Hudson, next to the agency's boardroom -- 17 years from now. We'll see if that ends up being the case, but that aside, at least Koenigsberg has a vision based on the permanence of his agency's culture and has tied it to a physical space. And in this day and age, that's positively elemental.

On a personal level, I responded by telling Koenigsberg why Varick Street was so important to me.

"My first full-time job was working for my family's printing company on Varick Street in the early 1970s when it was printer's row. I became a Teamster at the age of 15, learned how to run an offset press, strip plates, operate a photostat camera system, and most importantly, that I needed to go back to school and finish my education," I explained, adding, "I always retained a fondness for the neighborhood and have watched it evolve into a digital and advertising services Mecca" and that some of my favorite impressions were meeting with him in his conference room looking out at the Hudson and listening to him talk about his plans for the future.

In the weeks that have followed, I've thought a lot about the legacies of media agency brands -- both holdcos and independents -- and I'm not sure why, but the demise of GroupM's really hit me personally, because I've spent so much of my career writing about it.

I actually didn't know how much until a few minutes ago when I ran an internal search of my MediaPost bylines and found that since joining MediaPost in 2003 -- the same year WPP founded GroupM -- I have written 775 articles about GroupM. That's more than twice the number of bylines I've had writing about the next most-covered agency media brand, IPG Mediabrands.

I'm not sure why I've written so much more about GroupM over the years, but at least part of it was that it did two important things that the media shops did not:

• It continuously innovated.

• It spoke publicly -- or at least to me -- about how and why it was innovating the marketplace.

In retrospect, though, I think there was a third even more important element contributing to the attention I devoted to GroupM over more than two decades: the people who have led it -- from its visionary founder Irwin Gotlieb through digital and experiential native Christian Juhl. I'm not going to say they have been cult-like leaders, but they -- and most of the other media agency leaders I've cared about covering -- at least had a personality and a message I cared about covering.

I can't say the same thing is true of many others, and while I'm not going to name names on which media agency leaders were lacking, you can look at the chart above and guess for yourself.

Look, in the end, I know this is a relationship business, and a big part of why a trade journalist writes about one executive and his organization and not another is because they actually have a relationship.

But honestly, not all my relationships with the people I cover have been good ones, they were just interesting people doing interesting things that I thought were interesting to our readers.

For nearly half a century I've written about some of these characters, because they were something special. I think some of them liked me. I think some of them didn't like me. And I can tell you for a fact that a few of them have blackballed me.

But the one thing they all had in common, was a colorful personality that made me want to write about them.

I as lucky that when I started out covering the agency business in the early 1980s there were so many colorful characters running the ad business. Not just media wonks, but full-service/creative ones like George Lois, Jerry Della Femina, etc. But it wasn't just the larger-than-life characters, but some behind-the-scenes, business thinkers who were reshaping the agency world like a giant chessboard: IPG's Phil Geier, WPP's Martin Sorrell, Havas' Rodés family, and yes, even Omnicom's John Wren.

But to me, the pure-play media entrepreneurs always were my favorite subject, and I was tickled to recently write about yet another new act for one of the pioneers, Dennis Holt, who like Koenigsberg continues to have strong vision of the future. And not just techspeak buzzword bingo, but the culture that makes a strong, differentiated, sustainable and growing media services organization.

There are so many great personalities I've had the opportunity to cover and get to know -- not just Koenigsberg and Gotlieb, but the Verklins, Farellas, Lotitos, Kostyras, and I can go on.

But the one thing they all had in common was a personality that was framed around a unique and differentiated sense of media service culture.

And if all of them have a new modern day heir, it's probably PMG's George Popstefanov.

He reminds me very much of the young and hungry Koenigsberg I met back in the late 1980s and is definitely someone to keep an eye on for the future.

Like Koenigsberg, he can talk about tech, data, clients, etc., but what he really likes to talk about is his people and his organization. Sometimes real estate too.