476. What’s significant about that number? Well, it’s a Harshad number. Math geeks can learn more here. For history buffs, it’s also the year when we switched from the Julian to the Anno Domini calendar. Generally, it’s when most historians say the Roman Empire fell and we went from ancient history to the Middle Ages.

It also happens to be the number of Search Insider columns I’ve written since my first appearance here 10-and-a-half years ago.

It’s been a good run. I’ve had fun. I’ve ranted the odd time. I’ve taken you with me on my family vacations. Most of all, I’ve had a ringside seat at the emergence of a true industry. In fact, that’s what my very first column was about: search growing beyond the confines of a cottage industry into a real contender for ad budgets. Here’s how I ended that column:

Search will become much more sophisticated, and the price of entry to play the game may prove to be too expensive for many smaller providers. Alliances will form and total solutions will begin to emerge. Google and Yahoo! will have to address the huge amount of time and effort required to manage a large, sponsored search campaign. Real money will start to be invested and made.

And to think, one day I'll be able to say I was there.

Well, I guess that day has arrived. In the next five years, according to Forrester, digital will surpass TV as the single biggest destination for marketing budgets, and search will make up the lion’s share of that spend. Digital budgets combined are forecast to top $100 billion. I think that qualifies as “real money.”

But regular readers will also know that over the past 10-plus years, my columns have spent less and less time inside the “Search Insider” box. I’ve talked before about the artificiality of the way we’ve divided online up into channels. As our digital world has become richer and more robust, it’s become increasingly difficult to keep it compartmentalized into arbitrarily defined boxes.

My personal interest has always centered on human behaviors and the rapidly growing intersection between behavior and technology. Search is part of that, but so is social and mobile and content, and rich media and wearable technology and -- well, you get the idea. Digital is a deeply and widely interwoven part of our lives. It makes up much of the context of our environment. Trying to talk only about one part of it would be like trying to describe the world by only writing about water.  

At the end of 2014 (AD – just to keep our calendar references consistent), Ken Fadner, the publisher of MediaPost, asked me if I’d consider a move. I said yes. So this column -- number 476 -- will be my last one for the Search Insider. Starting next week, I’ll join the Online Spin lineup.

It’s probably more appropriate. I haven’t been active in search marketing for the last two years, so  I’m hardly an “Insider” any more. I am, at best, a somewhat informed observer commenting from the sidelines. I think that can still be a useful perspective.  I will continue to write about the things that interest me: corporate strategy, human behavior, evolving cultures, digital technology -- and yes, the odd rant.

So, for those of you who have been along for the ride for the last 10-and-a-half years, thanks for sticking around. When this ride started, there was no Facebook, no iPhone, no YouTube, no Twitter -- and Google was just starting to figure out how to make some real money.

We’ve come a long way. But I suspect we’ve barely started.  Maybe we’re even transitioning from one era to another. After all, it’s happened before when we’ve hit the number 476.

See you next Tuesday at Online Spin.