From wayyy back in the day (circa ~'99), something my friends and I built along the same lines: http://www.imood.com/ It had a shockingly passionate user-base and is still kicking along with a fair number of users. Originally all in kludgy CGI and perl!
That's awesome, love the domain name. You got a nice list of moods / emotions; it took us a long time to just pick 9.
Do you do any crazy reporting - like the average mood of a Monday compared to that of a Friday? I think that stuff could be really interesting, which is partly why we built moodbeat.