I don't think Zuckerberg will go, though I'm sure Facebook would like to send him. This puts them in a bad spot. To show respect, Zuckerberg should go. But then

I don't think Zuckerberg will go, though I'm sure Facebook would like to send him. This puts them in a bad spot. To show respect, Zuckerberg should go. But then it sets a precedent that every country can summon him at will and it becomes an insult if he doesn't show up. And there are enough countries and committees that would enjoy ordering a US megacorp executive around, that it has a real risk of becoming a problem. They'll probably send their highest level UK exec, or US exec that serves in some kind of ambassador role. Edit: Plus, if Zuckerberg screws up and says something he shouldn't or commits to something he shouldn't, Facebook has no recourse. If they send a representative, that representative can always be deemed to not be properly representing the company, the statement can be clarified, and/or the representative can be chastised or replaced.