The language barrier thin is very real. I'm not a native English speaker and have very hard time understanding people with heavier accents. It's especially bad over phone/web conference.

Also it's really amazing how crappy many companies' web conferencing setup is. They break down regularly, have poor sound quality and are generally really flaky. I know this is getting better with Hangouts and alike, but still, they are occasionally going to crap out and always, it seems, at the most inopportune time.