Regarding versus Facebook status. Facebook status will move very fast. If you post "I want to go and see Batman" in a couple of days time everyone will have forgotten about it. This keeps track over time.

Initially we planned it to have tight facebook integration but the facebook api proved to be an enormous pain, so we cut our losses to built what we could build in a weekend.

Also we wanted an android/iphone front end which would be good for realtime activities (i.e I want to go to the pub this evening) but again it was a time thing.