Today, Twitter announced that instead of the normal timeline of newest messages on top, they will prioritize messages they think you'll be interested in. This angers a lot of people, but my guess it's it's something Twitter has to do.
Let me give you an example. Edward @Snowden has 1.4 million followers on Twitter. Yesterday, he retweeted a link to one of my blogposts. You'd think this would've caused a flood of traffic to my blog, but it hasn't. That post still has fewer than 5000 pageviews, and is only the third most popular post on my blog this week. More people come from Reddit and news.ycombinator.com than from Twitter.
I suspect the reason is that the older twitter gets, the more people people follow. (...the more persons each individual Twitter customer will follow). I'm in that boat. If you tweeted something more than 10 minutes since the last time I checked Twitter, I will not have seen it. I read fewer than 5% of what's possible in my timeline. That's something Twitter can actually measure, so they already know it's a problem.
Note that the Internet is littered with websites that were once dominant in their day, but which failed to change and adapt. Internet oldtimers will remember Slashdot as a good example.
Thus, Twitter has to evolve. There's a good change their attempts will fail, and they'll shoot themselves. On the other hand, not attempting is guaranteed failure.