One could argue that this is something they should have thought about earlier, a fairly bitter pill to swallow as Twitter itself has been built on the backs of third-party innovations (such as hashtags). The ‘gain users fast, THEN figure out a business model later’ approach has led to an outcry amongst Twitter client developers. The real competitor to Twitter right now, is actually Google+, which by contrast does not rely on displaying advertisements alongside content.
Here’s a good food analogy: http://bits.blogs.nytimes.com/2012/08/24/twitter-developers-and-the-food-trucks/
“Twitter has stopped caring about the users that made the service popular, and started only to care about the users that can draw in more users. Twitter has sold out. They not only don’t care about the original users, but they don’t even seem to care much for the current users — there’s a very real sense that Twitter needs to make money, and they need to make that money yesterday. The people that really cared have moved on — either to new companies (Square and Medium) or simply moved on to something else.”