By lingo! Speak local, please

I visited a friend last week who works for a Chinese company. While I was there, her Chinese colleagues were doing various tasks around her. And they were all speaking Mandarin.

My friend, who speaks some, but not much, Chinese said something to the effect: "Could you please speak English so I can feel included in this conversation?" Her colleagues ignored her and continued speaking in Chinese.

Certainly there are a number of non-Mandarin speaking foreigners here working at domestic and multinational companies with Chinese colleagues who do not speak English around them. Should they? And how does it impact the office environment - relationships, trust, for example - if they don't?