Reading the mood page got me thinking about emoticons and how to potentially represent these, particularly in status updates.

There are some common emoticons like

• :) - smile
• ;) - wink
• :( - frown

For services that communicate mood, since it might not be desirable to include images with every update (and have them rendered), a possible way to encode mood (or as a fall-back) could be to use common emoticon representations.