I just read a very interesting article on Facebook negotiating to acquire Twitter.
The analysis of why this deal failed from a business perspective is important and informative - issues such as ad revenue, SMS fees, etc. - as these are important issues related to sustainability (which I still fret are not given enough attention in the ICT4D field). The article is also interesting in the way it discusses differences between social networking (Facebook) from microblogging (Twitter). It's always good to have one more explanation.
From my personal perspective, as a user of both services, I'm glad the two companies are not getting together just yet. I use them for different purposes, and more importantly I think Twitter has gotten better at one particular thing by being focused ... a focus that might get lost in the "bigger picture" of social networking. My hope is that Twitter becomes even better yet staying focused and independent.