If it's your boss, or one of your critical colleagues,
    maybe.

I'm surprised a few people pushed back on my assertion that it's okay/normal to have coworkers synchronously contact you several times per day. Are there a lot of engineers who are able and permitted to work for entire days on end, totally "dark" without some realtime pings from coworkers?

    If it's some idiot in a distal group trying to 
    justify their existence by being vocal

I'd certainly agree here. An old manager of mine referred to these sorts of outside-the-group disruptions as "drive-by shootings."

I have always liked that phrase. Those disruptions are definitely a great way to unexpectedly murderer productivity.

You need cross-group pollination, but random productivity-murdering drive-bys are not the way to do it.