We discussed this earlier but I thought it made sense to create a thread here.

In particular, it should be logged when a user is online. Now with that information, we can do a few things:

1. track how many users are online site-wide
2. show when a user was last online on their profile

anything else?

in my opinion, tracking last message sent is more meaningful in each profile and it's easier to instrument

in general i don't like exposing online time anywhere, ever

for statistics, there could be a panel saying: last week we've seen activity from 4 peeps ! awesome !

also, each thread could have count of overall people that ever visited it as well as in last X period time