Client-serving is very different, and I'm sure a good CEO would insist that you take the call rather than be in a meeting. I was thinking more about from the developer angle, so I guess I should have been clearer.
Like I said below, interrupting a meeting and leaving to take a call from your mechanic because your car is ready, or from a friend to plan your activity that night, is rude, and I've seen a lot of that.
I still don't agree. I think it's important to realize people can't always separate their work and personal lives -- especially things like taking a call from a mechanic at 11:00am. I wouldn't expect people to make all of their personal calls at 6:01 every day since it's generally not practical. I say this from a management perspective where I used to be pretty demanding about attention. After a while I realized that sometimes your team has to take that call from their vet. I think letting your team make that decision for themselves goes a long way in building a relationship.
I kind of see it like this:
You're either in an "all hands" type meeting or a small group or two-person meeting. If it's the former then I think participation is completely optional as you're likely to get a recap from a colleague afterwards or via email. If it's the latter then you're likely to be a relatively important part of that meeting and the others can wait for you if you need to interrupt. Of couse that doesn't mean that you should take every call whether business or personal but I don't think it's a case of either/or. There are plenty of company-related calls that could be temporarily ignored and vice-versa.
Like I said below, interrupting a meeting and leaving to take a call from your mechanic because your car is ready, or from a friend to plan your activity that night, is rude, and I've seen a lot of that.