Depend what do you mean by worth. If you mean earn, I think it is worth for affiliate business but it kind less worth for google adsense.
IMHO, Twitter is a fad - a year or so from now it wont be near as popular as it is today - and 2 years, you'll be like "Twitter? that's soo 2008".. I think that Facebook, although not a 'fad', will also wain in popularity. Look to ancient history as an example: anyone remember Myspace and how wildly popular it was 3 years ago? It was going to rule the world.. and NOW look - everybody laughs at it. So, IMO, i would not spend much time/effort on it - you're too late. Had you gotten a head start 2 years ago, you might do well today. Spend your effort looking for what will be popular a year from now and get a head start.