Both have their respective strengths. I like (or maybe that should be "liked") the privacy of Facebook that allows me to communicate and stay in touch with friends and family, and I like the relative anonymity and ease of use of Twitter. I wouldn't use Twitter for my more personal interactions - I use Twitter a little for this, and on a very casual level, but for the most part in a more detached way, spotting trends etc. Having said that, I must say that FB's recent interface changes have made their home page vastly less useful to me (less privacy, less insight into friends' connections), and actually made me investigate Twitter in the first place. Now I hardly ever look at FB's home page anymore, and spend more time Twittering and getting on with my life. Heckuva job, Zuckerberg.