Happy sixth birthday, Twitter! You’re the service which started off as a way for groups of friends to keep in touch with each other via text messages, and you’ve grown into a revolutionary platform for connecting and sharing with millions of people around the world.

And you’ve become more annoying, too.

For most of its history, Twitter was disliked overwhelmingly by people who weren’t on it, rather than people who were. It wasn’t enough not to join; if you weren’t on it, you had to kvetch incessantly about how you weren’t interested in what other people were eating for breakfast.

I’ve noticed a change, though, in the past year. The people who used to complain the most about Twitter have either capitulated and joined, or else they’ve quietened down — at least they know, now, how infrequently anybody tweets about what they are eating for breakfast. And now the primary source of complaints about Twitter is coming from people on Twitter, rather than off it.

During SXSW, for instance, there was a steady drumbeat of people on my timeline complaining about all the tweets from SXSW. (I was there, and even I got annoyed by the endless banal SXSW tweets; I’m sympathetic to their plight.)

We’re going to have to live with many more annoying tweets going forwards, if things like Amex’s “tweet your way to savings” campaign take off. The VentureBeat headline is “American Express transforms Twitter hashtags into savings for cardholders,” but another way to put it is that American Express is trying to make money by getting people to spam their friends with hashtags like #AmexWholeFoods which have no value to the reader whatsoever.

And then there are people like Porter Versfelt III, who will get annoyed if I dare to express a personal opinion on Twitter. For Mr Versfelt, I have a “core purpose” on Twitter, which is to provide him with financial news, and anything I do outside that purpose is annoying.

Going forwards, all of us are going to find Twitter increasingly annoying. The company has been in hyper-growth mode up until now, getting to its current astonishing scale. But it’s now getting serious about making money, which means selling us, the users, to people willing to pay lots of money to work their way into our timelines one way or another.

On top of that, Twitter is increasingly going to be a medium for following people you don’t know, rather than people you do. When that happens, it’s much easier to get annoyed at what they’re tweeting, especially when those tweets are somewhat personal in nature (check-ins, photographs, that kind of thing). We neither can nor should try to stop people from tweeting whatever they want — the way that Twitter works, if you don’t want to read someone’s tweets, that’s easy, just stop following them. But at the same time, nearly everybody’s follower count is rising steadily, and as one’s follower count goes up, the more that Twitter becomes a broadcast medium rather than a medium of conversation. And when you become a broadcaster, you have to be more careful about what you say, or risk annoying a large number of people.

Twitter’s still in its honeymoon period, but that won’t last forever. At some point, it’s going to be less of a wunderkammer, and more of a regrettable necessity. Which is probably the point at which it’s going to finally start making some real money.

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Felix Salmon is an Audit contributor. He's also the finance blogger for Reuters; this post can also be found at Reuters.com.