I think showing your face on your blog or website is an effective way to build confidence and trust online. I see that there are a lot of people using avatars nowadays. Most are only approximate, sometimes caricatured, representations of people’s photos. Personally I don’t think avatars can replace your real photo. Do avatars have any real value for building trust online or are they just for amusement?
I look at them like a logo/brand. It’s a visual way for others to recognize you. Do they add to ones trust by themselves? Probably not but neither would an image of someones face. Trust is earned by ones actions then that would be attributed to the avatar, so to speak.
I use them as a quick visual id of the author. It’s easier to recognize a familiar avatar than it is to read each name. I guess whether or not it should be something “fun” or something “realistic” depends on where you use it and the image you want to project. Of course how you interpet the image will vary from how any other given individual interpets it, but I think they could be used to convey a “general feel or tone”. And as BPartch said, what you post next to it carrys a lot more weight than the avatar does.
People recognise and remember images more than words, it’s been scientifically proven that visual memory has an easier time of being converted to long term memory. Therefore the use of an avatar gives people a visual recognition point to recognise another user… it’s almost in the same way that you’re more likely to remember a person if you meet them face to face (and form that association) than if you just talk to them on the phone. It’s a case of unique identity being established (which is a good thing) and aids the readability of the content on the basis that people spend less time trying to work out who wrote what and focus solely on what they wrote (even if their avatar is a cartoon it still has the implied impact). And any navigation aid which speeds up the process is a good thing if you ask me! 
I believe that the use of a photo on a website will help build trust…too many site are impersonal and cold…
I would put my photo as my avatar. To let people, especially prospective clients, see the face behind the name.
I want to be seen as a person who can help, not a giant corporation who is stuck in red-tape.
I think avatars are best for the admin and special authors of sites. avatars aren’t seen as good or bad, but it just depends on the person whether they use one or not.
Agreed - for me, it’s all about building my brand. My avatar is consistent everywhere I go on the internet, and that is an easy way for others to quickly identify with me (and my brand name).
IMO too, avatars help identifying people from a crowd. It is almost similar to the fact of uniqueness of each person on earth that helps to remember them separately. & definitely visual memory is also one reason.