Skype. The only missing thing is skype.
I think Facebook would be able to replace skype quickly (since everybody have Facebook), but not Google.
1. I did a statement that people who need skype won't buy it. 2. Someone told me that "these things have hangout instead". 3. I pointed that it doesn't matter since all your contacts are still in skype (and their contacts too), so you'll have to switch them all to hangout too. 4. Now you're saying "If they have a Chromebook, it's a good bet they have a Google account".
How is it related at all???
If all my friends, all my colleagues, and all my clients are on Skype, then having an alternative doesn't help at all.