I agree, it's not a "must."  But if you do it, I think you'll find it has deeper benefits than just fame and career advancement.  My own blogging is about fun hacks that are educational for me but unrelated for my work.  Blogging helps me learn better, because:<p>- Explaining things forces me to understand them better.<p>- Wanting to share what I've done motivates me to finish it.<p>- Comments from others teach me things I didn't know to look for myself.