Twitter sparked widespread outrage when it added an ad-serving banner to its iPhone application that quickly became known as the dickbar. Regardless of whether you love it or hate it, some of the outrage has completely missed the mark. Twitter has always been a free service and some now argue that the dickbar was an inevitable result of Twitter needing to make money. Avoid all free servcies, say the dickbar haters.
Fortunately or not, it's not so simple. Twitter could have implemented a better ad-serving feature or found another way monetize its growing user base. And plenty of not-free services have added unwanted and undesirable "features."
Among the many counter-examples, enter Angry Birds maker Rovio. The version of Angry Birds that runs on Apple's iOS devices like the iPhone has always been a paid app while the Android version was free with ads. Then Rovio decided to add ads to the iOS version, sparking a storm of criticism that paid versions can't possibly have ads.
Who knows whether Rovio will back off -- I suspect not -- but the learning point for software and web service users everywhere is clearer. It's not free or paid that makes a difference. It's a much less obvious stew of the sustainability of the business model, the greed of the app writers and the value of the product they supply. Free can become paid. Paid can become more paid (hello, Mozy!). There are no guarantees and there's no free lunch.