Snapatar is a simple page with one purpose. It prompts you to allow flash control and access to your webcam and then your Twitter username and password. While I wished they would use oAuth, they don’t as of yet. They do address it in the FAQ:
No OAuth? Is this safe?
The short answer is yes! Snapatar was built using Flash, which makes OAuth a little more complicated to implement. Snapatar does not store your password in any way or share it with anyone.
Once you grant access to your webcam for the session, you click the big yellow Snap button and it takes your picture and uploads it to be your new Twitter avatar! You can set a timer with it and even mirror the image in the advanced settings.
They had the current stats listed but I am hoping we can help them blow it away
Total avatar updates: 256 (108 users)
Tweets sent: 164 (64%)
By default it does have a button checked to send a tweet alerting everyone you used the service to change your avatar, but they allow you to uncheck it, so no huge deal.
Lastly, there is a help balloon but it is not active until you allow camera access. I wish they had a link somewhere with some About information well before I used the service, but we did it for you as usual!