Eh, its your choice.
I tend not to put pictures of me online as:
a) I tend to avoid cameras. The most recent picture of me is probably around 3 years old by now.
b) I favour privacy online. Same reason I'll usually not put my name online, even on "Official" things - where I'll just make up a fake name. I don't like people I don't know knowing who I am in any regard.
c) I'm lazy and its far more effort for me to get a picture off a camera onto my PC, then upload it as a profile pick than it is for me to type in "Cylon", "Gandalf" or "SOPA Shall not Pass", grab a URL link, and set that as my avatar. As you can probably tell, I CBF even doing this that often - my avatar is still going on about SOPA when that's old news by now. I just CBF updating it.