While the mainstream media is carrying the news of Twitters great losses, the fact is that it is making great losses mainly because it is offering free webhosting to all,and most people do not realize that webhosting is very expensive
Anyone who has actually run a website realizes that the cost depends on the size of the database, and the web hosting company will charge more money if more web server space, and more bandwidth is used.
Twitter is only exploring advertising to monetize the website,and online advertising is highly manipulated, some publishers are not making even $1 a month from PPC and CPM advertising despite having thousands of visitors
So one of the most effective methods to make some money for Twitter and other social media websites, is charging users based on how much resources they are using.