Like Facebook, Twitter makes its money primarily by selling ads, which gain a lot of their value from the advertiser's ability to target specific groups of users. Twitter's disadvantage relative to Facebook is scale: It has on the order of 200 million users, while Facebook has some 1.15 billion. But its advantage lies in timeliness and topicality. People check Facebook casually, when time allows. Twitter users tend to use Twitter quite actively, and in conjunction with specific events, like TV shows, rallies, concerts, and breaking news. So advertisers can craft ads tailored not only to a Twitter user's general tastes and demographic profile, but to what that user is doing at the very moment they see the ad.
Twitter's advantage is speed and hyper-relevancy, not to mention the people you follow are way more interesting than your friends in Facebook. You can also treat it like an RSS feed if you wish.
Twitter is really multidimensional because it grew up on the mobile phone, the reverse of a majority of all the other social networks minus Path. It's not a desktop product by any means.
Give me some stock.