"definite must"? If I find a successful developer, for some value of successful, that doesn't blog, would that prove your friend wrong?<p>You need to decide what your goals are. Are you striving to optimize your career for followers/notoriety? Than yeah, having a blogging/twitter/social media presence is a must. If you're striving to optimize your life for maximum profits and earnings, than having an online presence can help, but is probably not a must. If you're striving to become a great developer/programmer and are doing it for the love of the craft, then spending time blogging/twittering/etc will probably get in your way.