Forum Moderators: phranque
On one hand, you are offering your visitors reasons to ignore your forum by having multiple chats going, etc.
OTOH, by making this communication easier, you may boost your forum's use as a permanent hangout for your target population and gain advantage over forums that don't offer it.
I've got one busy forum frequented by users of teen years and beyond, with a hefty late-teen population. These users are IMing constantly anyway, so I'm not sure that facilitating it would negatively impact the forum quality or traffic.
Any other pros & cons and/or salient commentary?
My forums all allow users to display their various IMs, but for me, I don't use that feature on a forum and only give my IM addresses out to people I want to ;)
You could also offer a general chat room for members as well - this can also go a long way to keeping people on the site, and keeping them returning as well.