While an individual user may use Twitter primarily as a conversational tool or a broadcast medium, in its totality, Twitter operates a lot like a wiki: as a knowledge-sharing, co-creation platform that produces content and allows its consumption. Conversation is perhaps the most simple and obvious form of collaboration, but would anyone claim that Wikipedia is a conversational platform? Despite the presence of information sharing, co-creation of an end product, and even discussion pages, Wikipedians on the whole aren't having conversations. According to this argument, Twitter is no more a conversational platform than Wikipedia is.
While Twitter has been less than forthcoming on how they plan to monetize their service, there is no shortage of ideas from third parties on ways to get paid for spending time with Twitter.