(Moved here from comment)
Most MUAs (mail reading programs) do not allow by default (for good reasons) the fetching of external images --- it would be a big privacy problem otherwise. The normal behavior should be the one you comment, and you have to actively load external images to see them.
It's just a nice and stylish way of showing off.
Flair exists to let everyone else know about your brilliant Stack Exchange profile. You should put it on your website, your page on the Ubuntu wiki, and your vest that you wear at work.
Brian, for example, has 37 pieces of flair (and a terrific smile)
The URL of your flair is http://askubuntu.com/users/...