This seems similar to the problem solved by Gravatar with their automatically generated avatars, as well as similar services like robohash[1].<p>[1]: <a href="http://robohash.org/" rel="nofollow">http://robohash.org/</a><p>I've used several sites like StackOverflow that use the automatically generated images from Gravatar, and they really do make the site more pleasant. Additionally, they make it easier to visually follow who posted what in a discussion.<p>The one difference (unless I misunderstood the article) is that these sorts of images are generated randomly from a hash and so are basically guaranteed to be unique. I think this is a big advantage as having two identical avatars in a discussion would just make it visually confusing to see who is who.
A little trick I learnt from a fellow designer: Make the default profile pic the opposite gender from what you guess the user to be. Users are fine staring at an androgynous avatar but they'll rapidly upload their own pic to avoid others thinking they're a woman/man.
This is insightful especially since we have thought about this problem and had not come up with a solution. I am assuming all the icons will be unique though, else it may lead to a lot of confusion. Also, I believe people choose icons that they best identify with and if it is not unique their association with the icon may not be as strong.<p>Another thing I have experimented with is if you can upload a picture and create a hand drawn painting / image like Chris Dixon's or Fred Wilson's image which I think are brilliant in creating a brand and identity.
I'm not sure if it is still the case, but HypeMachine used to have their default avatar be an angry looking picture of Dick Cheney.<p>I can only imagine the number of people rushing to upload their own image in place of our former veep.
Or do something cool with the default. At the NASA astrobiology institute they have little astronaut silhouettes for the default profile pic:<p><a href="http://astrobiology-beta.arc.nasa.gov/directory/carey-sean/" rel="nofollow">http://astrobiology-beta.arc.nasa.gov/directory/carey-sean/</a>
They look very much like the original Mac OS icon/face.<p><a href="http://upload.wikimedia.org/wikipedia/en/8/81/Mac_OS_Logo_with_Text.svg" rel="nofollow">http://upload.wikimedia.org/wikipedia/en/8/81/Mac_OS_Logo_wi...</a>
Have the highest respect for the folks at 37signals, but this is definitely not a HN frontpage worthy post. I'm beginning to see almost every blog post by them on HN front page. No offense but it doesn't kindle the hacker's knowledge in any way.