One of the exercises I have introduced in my workshops is taking a before and after headshot and getting the audience to guess the vocation of the individual.
There seems to be several schools of thought out there at the moment as to how you should present yourself in terms of picture in online profiles. I have seen a number of leading social media experts advocate the use of the same photo for all accounts.
Personally I like to see different pictures of people depending on the social media point of interaction. I certainly do this, with a picture of my presenting taken complete with LinkedIn logo in the background for my LinkedIn profile and a very similar one for my gravatar on blog comments and responses and a presenting one on my Facebook fan page.
For 'standard' Facebook I use a more personal picture that has raised a number of comments as well as recognition from friends and relatives.
Which ever way you decide to go, ensure that the picture(s) you choose are a good reflection of you and your personal brand (no airbrushing etc!) and that they appear relevant to the medium in which you are displaying it.
What do you think? Does your picture reflect who you are?